The Seattle Mariners’ biggest offseason need is obvious.

While the club would benefit by adding another reliever or a regular outfielder, the Mariners must improve their rotation. Otherwise, they’re destined to start the new season the same way they finished in 2016 — as a fringe contender.

Optimally, Seattle would add two starters with one being a top-of-the-rotation type. Having said that, acquiring a top pitcher is unlikely. There are no free agents ready to fill that role and the Mariners will be challenged to match or beat the competition’s offers in the trade market. At the very least, the team needs to add a reliable mid-rotation arm capable of going deep into games.

To date, general manager Jerry Dipoto has added two new starters to the mix — Chris Heston and Rob Whalen. But, both pitchers represent depth pieces behind holdovers Felix Hernandez, Hisashi Iwakuma, James Paxton, Nate Karns, and Ariel Miranda rather than a middle-of-the-rotation solution.

Based on what I’ve read on social media, a segment of Mariners faithful doesn’t necessarily believe the club needs to acquire another pitcher — let alone two — to be a serious contender. They optimistically believe the seven pitchers already mentioned can be as good a last year’s top rotation candidates.

Perhaps those fans will be right, but there are reasons to believe otherwise. Please let me explain.

Last year’s rotation was better on paper
At this point last year, the Mariners had Hernandez, Iwakuma, Wade Miley, and Taijuan Walker as their top-four starters with Paxton and Karns set to compete for the final rotation spot and Mike Montgomery lurking in the background as a fallback option.

Since July, three of those pitchers — Miley, Montgomery, and Walker — have been traded and replaced by Miranda, Whalen, and Heston. On paper, these moves do not represent an upgrade or even swap of talent.

Using Steamer projections found at FanGraphs and their version of wins above replacement (fWAR) as references, the Mariners’ current starting staff doesn’t project to be better than the one assembled by Dipoto just 12 months ago. To see what I mean, look at the following table.

 January 2016 Rotation January 2017 Rotation
Name 2016 Steamer 2016 fWAR Name 2017 Steamer
Felix Hernandez 4.7 1.0 Felix Hernandez 3.1
Hisashi Iwakuma 2.9 2.4 Hisashi Iwakuma 2.5
Taijuan Walker 2.4 0.6 James Paxton 3.6
Wade Miley 1.9 0.6 Nate Karns 1.7
Nate Karns 1.3 1.3 Ariel Miranda 1.1
James Paxton 0.8 3.5 Rob Whalen 0.2
Mike Montgomery 0.1 0.1 Chris Heston 0.1
Totals 14.1 9.5 Total 12.3


Before going any further, I have to acknowledge that projections are nothing more than estimates based on factors such as an individual’s playing history and age. Since it’s impossible to forecast injuries or when aging players might fall off the proverbial cliff, projections are imperfect by nature.

Still, in this case, these estimates provide us some context on whether 2017 rotation measures up to last year’s group — they do not.

The 2016 rotation was inadequate 
Even if this year’s starting staff was the equal of the 2016 version, that wouldn’t be good enough. Let’s take a moment to refresh our collective memories on the struggles of last season’s rotation.

Hernandez missed nearly two months due to a calf strain and was uncharacteristically inconsistent throughout the year. Before the season, many observers thought Walker was ready to fulfill his potential as a future ace. Instead, he too struggled with injury and inconsistency.

To compound matters, a pair of starters acquired during Dipoto’s biggest offseason deals didn’t produce — at least not on a regular basis.

The Mariners expected Miley to stabilize the middle of their rotation and provide quality innings. But, he proved to be inconsistent and suffered a brief bout of shoulder soreness. By July, management determined the southpaw wasn’t a good fit for their club and traded him to the Baltimore Orioles.

The other major pitching acquisition — Karns — outlasted Paxton for the last rotation spot in Peoria only to lose his starting gig after failing to reach the sixth inning during four of five starts in June. Seattle relegated the 29-year-old to the bullpen before he suffered a season-ending back injury.

Not everything was doom and gloom for the starting staff. Iwakuma proved to be reliable and was the only pitcher from the Opening Day roster to make every scheduled start, while Paxton’s brilliant potential began to emerge after replacing the injured Hernandez in late May.

Going deep matters
In retrospect, Karns’ struggles to reach the sixth inning in June underscore the Mariners’ difficulties during that month and throughout the season. When the rotation didn’t deliver innings, Seattle didn’t fare well in the win-loss column.

Going Deep Matters
Month # Games SP Reached 6th
Monthly W-L
April 17 13-10
May 20 17-11
June 13 10-18
July 17 12-12
August 22 16-14
Sept/Oct 20 18-11
 Season Totals
109 86-76


In all likelihood, the struggles of the Mariners’ rotation prevented them from reaching the postseason in 2016. By simply posting a .500 winning percentage in June, Seattle would’ve placed ahead of both 89-win wild card teams.

Sure, the bullpen scuffled and their overall defense was below average. Those factors can’t be overlooked. But, the Mariners’ run-prevention difficulties were firmly rooted in their starters’ inability to pitch deep into games during different points of the season.

A comparison of the Mariners’ win-loss record, based on the final inning the starter took to the mound, further illustrates the relationship between the resilience of the starting pitcher and the team’s success on the field.

Seattle’s Record Based on Inning Started
Innings Pitched
Games Wins Winning Pct
Into 6th
109 74 .679
Into 5th
35 11 .314
Into 4th or less
18 1 .056
Season Total 162 86 .531


It’s not shocking to see that Seattle did well when the starter reached the sixth inning — even if he didn’t register an out. But, the club’s lack of success when the starter couldn’t finished the fifth frame was staggering. If the starter didn’t complete the fourth, the Mariners had a win-loss record similar to that of the Cleveland Browns.

Some of you may be wondering how the rest of the American League fared when their starter began the sixth inning. The following table answers that question with the five postseason teams highlighted in yellow.

Teams That Went Deep (2016)
Team Games Into 6th Wins PCT
TOR 132 79 .598
CWS 127 68 .535
BOS 122 73 .598
NYY 119 67 .563
CLE 114 80 .702
TEX 114 77 .519
TBR 110 53 .482
SEA 109 74 .679
HOU 107 64 .598
KCR 107 62 .579
LAA 106 55 .519
OAK 105 58 .552
DET 105 65 .619
BAL 103 67 .650
MIN 98 50 .510
League Avg 112 66 .591


Every team, with the exception of the Texas Rangers had a better winning percentage when their starter reached the sixth. The Rangers finished the season at .586 and the best record in the league.

The Orioles were the lone playoff team below league average in games (103), but they were at the league average for wins (67). I chalk that up to the fact they had a manager (Buck Showalter) with a penchant for pulling his starters early and an elite-level bullpen to lock down games.

After comparing the Mariners’ success to the rest of the league, my first reaction was they over-performed and aren’t likely to repeat their .679 winning percentage. This is where Seattle is most vulnerable to regression in 2017.

Since the Mariners don’t possess an elite-level bullpen like the Orioles, having a rotation capable of reaching the sixth inning more often will be vital to their success next season. Otherwise, the club risks ending the season with a .500 or worse record. Yes, the Mariners could have a losing record next season.

Who’s gonna go deep in 2017?
While some fans may disagree with my dim outlook and see a ray of hope with the Mariners’ .679 winning percentage, there are reasons to be concerned. Especially, when you consider who was going deep last season and the history of the replacements currently on hand.

Who Went Deep (2016)
Pitcher Starts 4th or less Into 5th
Into 6th
Hisashi Iwakuma 33 4 4 25
Felix Hernandez 25 2 4 19
Taijuan Walker 25 5 6 14
James Paxton 20 1 7 12
Wade Miley 19 2 3 14
Nate Karns 15 0 7 8
Ariel Miranda 10 2 0 8
Wade LeBlanc 8 1 1 6
Cody Martin 2 0 1 1
Mike Montgomery 2 0 1 1
Vidal Nuno 1 1 0 0
Adrian Sampson 1 0 1 0
Joe Wieland 1 0 0 1
Total 162 18 35 109


Two pitchers no longer with the Mariners — Miley and Walker — combined to reach the sixth inning 28 times last season. That’s 26-percent of the club’s total. Granted, each starter had disappointing seasons with Seattle. But, who on the current roster is going to fill the void caused by their departures?

Sure, Miranda did a nice job by reaching the sixth inning in 80-percent of his 10 career starts after coming over in the Miley deal and could potentially help. But, he isn’t even guaranteed to make the rotation out of Peoria. It’s conceivable that the southpaw may start the season in the bullpen or with Class-AAA Tacoma.

Heston had an impressive rookie campaign in 2015. He reached the sixth inning in 19 of his 31 starts and even threw a no-hitter. However, the righty started last season in the San Francisco Giants’ bullpen and was optioned to Class-AAA Sacramento by the end of April.

As a River Cat, Heston started 12 games before suffering an oblique injury in June. The 28-year-old returned to Sacramento late in the season, but was ineffective in two starts. The other new rotation candidate — Whalen — has five career starts and enters 2017 as a rookie. Certainly, this duo can’t be expected to eat the innings of Miley and Walker. At least not at the moment.

Unknown unknowns
Beyond the unproven nature of the “new guys,” Seattle’s top-three starters — Hernandez, Iwakuma, and Paxton — all enter next season with questions needing answers.

King Felix has publicly acknowledged he needs to improve his physical fitness and promises to be ready by the time pitchers and catchers report in February. But, he’ll be 31-years-old before the Mariners’ home opener. Will the right-hander continue on a path of decline or bounce back as Justin Verlander did with the Detroit Tigers last season?

Iwakuma was the rock of the Mariners’ rotation while throwing 199 innings last season. Having said that, the veteran has never tossed more than 180 innings in consecutive seasons during a 16-year professional career. Considering that he turns age-36 during the second week of the season, is it reasonable to expect him to break that trend in 2017?

The youngest of Seattle’s top-three — Paxton — appeared to finally break through after altering his delivery at the suggestion of Tacoma Rainiers pitching coach Lance Painter. Due to a rash of sometimes-freakish injuries, the lefty has started just 50 games since debuting in late 2013 — including 20 from last season. Will the 28-year-old continue his upward trajectory or will the injury bug continue to impede his progress?

Perhaps, the pitcher least mentioned — Karns — will bounce back now that he’s healthy. He’ll certainly get a shot to win a rotation spot. But, is it reasonable to expect the right-hander to be a regular six-inning fixture based on his first season in the Emerald City?

What now?
While I’ve learned to never underestimate the creativeness of Jerry Dipoto, let’s assume for a moment that a top-of-the-rotation arm is out of reach. That means the Mariners need at least one more proven arm to guard against possible declines by Felix and/or Kuma or a regression by Paxton.

With that in mind, I put together a table with potential candidates mentioned by Prospect Insider Jason A. Churchill right after the World Series and myself about a month later. As I did with the Mariners on the preceding table, I categorized their starts by the inning started.

Potential Mariner Targets
Pitcher 2016 fWAR Starts 4th or less Into 5th
Into 6th
Drew Smyly 2.0 30 2 8 20
Robbie Ray 3.0 32 2 13 17
Gio Gonzalez 2.9 32 4 4 24
Patrick Corbin 0.2 24 3 2 20
Josh Tomlin 1.0 29 2 7 20
Mike Leake 2.6 30 2 6 22
Ervin Santana 3.2 30 3 5 22
Dan Straily 1.2 31 2 5 24
Doug Fister 1.1 32 4 8 20
Ian Kennedy 1.7 33 2 3 28
Francisco Liriano 0.4 29 2 8 19
Jason Hammel 1.5 30 4 2 24


It’s worth noting that some of these pitchers are probably unavailable or out of Seattle’s price range. Having said that, wouldn’t all or most of these players be better options than the current collection of number-fives behind Felix, Kuma, and Paxton?

Perhaps, Dipoto can swing a trade for one of the names listed above and add a second starter — such as Doug Fister or Jason Hammel — via free agency. Doing so would create more quality and depth within the rotation. Remember, the Mariners used 13 starters last year and should expect to use a similar number next season.

The harsh reality is that the current Mariners’ rotation is fraught with uncertainty and is reliant on hope to succeed in 2017. Maybe my vision is being clouded by the dreary Pacific Northwest winter weather, although I don’t believe so.

Sure. If Felix is Felix again, Kuma remains healthy, and Paxton takes another step forward, Seattle will be in great shape. But, what’s the likelihood of all three scenarios happening next season?

Maybe Miranda exceeds expectations and turns the Miley deal into a steal or Karns has a bounce back year. Perhaps, Whalen or Heston will be pleasant surprises in 2017. If you’re a Mariners fan, how much money are you willing to bet on any of this taking place?

Could my grim outlook be completely wrong? Possibly.

If I’m right though, the Mariners are looking at another season of lingering at the fringe of contention without a clear path to the postseason. Wouldn’t that be a huge disappointment after their exciting 2016?

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Luke Arkins

Luke is a native New Yorker, who grew up as a Mets fan. After the US Navy moved him to the Pacific Northwest in 2009, he decided to make Seattle his home. In 2014, Luke joined the Prospect Insider team. During baseball season, he can often be found observing the local team at T-Mobile Park. You can follow Luke on Twitter @luke_arkins