Hisashi Iwakuma, Extension Candidate

Last week, news broke that Hisashi Iwakuma's $7 million team option had automatically vested based on his 2014 performance (probably an innings clause). It was assumed that Iwakuma would be a Mariner next year because the Mariners probably weren't going to decline such an advantageous deal. So, now that we have that administrative detail worked out, where do we go from here?

Before we knew about his option vesting, there were a few people calling for a longer extension for the Mariners' #2 pitcher. Even though he's already on board for next year, the Mariners could tear up his current contract and offer him a longer extension. Before we think about what an extension might look like, let's talk about Iwakuma himself and what the next few years may bring from him.

In my review of the Mariners' starting pitchers, I briefly examined what happened to Iwakuma down the stretch in 2014. In the second half, his ERA of 4.15 ranked 78^th out of 101 qualified pitchers and his ERA of 7.61 in September was the second worst in the majors. Such an uncharacteristic stretch from a pitcher who has been so consistently good over the last two years left many of us baffled.

He could have been dealing with some fatigue after missing most of Spring Training and the first month of the season with a finger injury. However, the two primary indicators of fatigue -- velocity and control -- looked fairly normal in September.

Strike zone percentage via Brooks Baseball:

Velocity, per pitch type via Brooks Baseball:

September seemed to be a just a stretch of poor luck for Iwakuma. His opponent's batting average on balls in play was a ridiculous .371 in September and his left on base percentage was 51.8%. Those two figures tell me that Iwakuma probably isn't toast and we just saw some extreme regression towards the mean in a very small window of time.

Besides the end of last year, Iwakuma has been remarkably consistent over the last three years as the Mariners' #2 starter.

His strikeout rate has been consistently around 20-22%, his walk rate between 3-7%, and he's lowered his FIP each year since moving to the rotation. His one weakness has been the home run but he's been able to mitigate that damage by refusing to allow batters to reach base.

He's heading into his age 34 season next year. What can we expect from him over the next few seasons if the Mariners were to sign him to an extension?

I ran a database search on FanGraphs to try and find similar pitchers who pitched at Iwakuma's level at his age. The parameters were 33-year-old pitchers since 1969 (the year the mound was lowered) with a strikeout rate between 18-22% and a walk rate between 3-7%. The search came up with twelve results. I omitted one result because it also occurred this year (Dan Haren). Here are the remaining eleven:

Note: Batted ball data is unavailable prior to 2002 so groundball rates and home runs per fly ball aren't included above for pitchers who played before then. Instead of HR/FB, I used HR/9 to give a better idea of which of these pitchers may have also struggled with the home run.

There are some pretty prestigious names on the list above. Roy Halladay's was nearing the peak of his career and Andy Pettitte carried the Houston Astros to the World Series in their age-33 seasons. The three Mikes (Mussina, Scott, and Krukow) seem to be the most similar to Iwakuma as far as these peripherals can show us. Curt Schilling also seems like a good comp but he was on the verge of becoming Curt Schilling in 2000. Koosman was in the middle of a long career -- he would pitch into his 40's -- so his durability was obviously an ability that Iwakuma hasn't been able to show. Ted Lilly might be a good comp but he was an extreme fly ball pitcher whereas Iwakuma primarily relies on the grounder.

Now let's see how the ten pitchers performed in their age-34 season:

Halladay, Schilling both had career years in their age-34 season and Mike Mussina resumed his previous, excellent career norms. The rest of the names continued to produce at a decent clip. Both Mike Scott and Mike Krukow continue to be a decent comp for what we might expect from Iwakuma in his age-34 season. So we shouldn't really be worried about Iwakuma in 2015. He'll probably put up numbers similar to the last three years, perhaps with a little bit of deterioration.

The most common length suggested for an extension for Iwakuma is three years. Let's take a look at the career path for these ten pitchers and see if we can see how they end up after their age-36 season:

Yikes. By age-36, Halladay had completely fallen apart and Loaiza and Scott had both pitched their last pitch in the majors. Krukow and Lilly had one more uninspiring year after age-36 before they retire as well. Just four of our eleven pitchers pitch beyond age-37 and three of them are Hall of Fame caliber (Pettitte, Mussina, and Schilling). If we remove these three pitchers from our sample, the remaining seven pitchers averaged 1.95 WAR per year between their age-34 and age-36 seasons. That's pretty uninspiring though not the death knell some might have expected.

If the Mariners are thinking about offering an extension to Hisashi Iwakuma, they must be convinced that he's a pretty special talent. With his injury history and the aging curve for his top comps, I'd say an extension is probably a pretty high risk. At the right price, an extension could make sense but I think that 2015 will be the last year Iwakuma will be paid below market value. Once he's a free agent, he'll probably be looking for one last payday before retirement and that could get expensive for the Mariners. His ability to stay healthy next year will go a long way to determining how much that free agent contract will be. Patience is the name of the game for the Mariners before they start thinking about committing to Iwakuma's age-35 season and beyond.