Tom Wilhelmsen has been an excellent reliever for the Mariners dating back to his promotion at the end of last July. Since the recall, he has posted an ERA and FIP south of three and a k/9 near 10, making him one of the most dominating relievers in the league. Wilhelmsen has solidified himself as the team's closer and he's turned the position into one of the few spots on the roster without question marks. But despite his success, and against all wisdom about fixing something that isn't broken, the Mariners might benefit from shifting Wilhelmsen to the rotation.
First, much of this is predicated on the development of Wilhelmsen's change up. Throughout most of his career, Wilhelmsen has relied on only two pitches, a fastball and a curve. For relievers, like Wilhelmsen, who rarely face hitters twice in one outing, two offerings are usually enough to thrive. But starters are tasked with longer assignments and it's difficult to fool major league hitters multiple times with only two weapons. There are very few starters in the league that don't have at least a show-me* third pitch, and it's unlikely that Wilhelmsen would have much success with his current arsenal.
*- A show-me is a pitch that a pitcher doesn't trust as much as his other offerings, and one he only uses a few times per game. While a pitcher generally won't throw his show-me in a critical situation, he'll employ it often enough to keep hitters aware of it. Jason Vargas's curve is a good example: it's not a terribly successful pitch on its own, but the threat that he might use it helps to set up his bread and butter change up.
Fortunately, so far so good for Wilhelmsen's change up. We're dealing with miniscule samples, but Brooks Baseball says Wilhelmsen has thrown twenty-six change ups this year, generating four whiffs and a few grounders in the process. I can't take anything overly encouraging from a sample of twenty-six pitches, but from all appearances, the change looks effective, and hitters certainly aren't pounding it yet. There's at least potential for the pitch, and considering that it's his number three offering, it only needs to be adequate. If we can accept the premise that Wilhelmsen might develop a usable change up, it then makes a ton of sense to consider using him in the rotation.
First of all, there isn't much risk in giving Wilhelmsen a shot. The club could stretch him out in Spring Training and evaluate whether his stuff translates to multi-inning duty or not without removing their closer from his role mid-season. If the move fails, they can always shift Wilhelmsen back to his previous job without directly affecting regular season games. And don't be dissuaded by the failures of guys like Daniel Bard (ineffectiveness) or Neftali Feliz (injury) in their switch from the bullpen to the rotation: pitchers get hurt and turn ineffective all the time for a variety of reasons. Heath Bell, Brian Wilson, Joakim Soria, Ryan Madson, and Sergio Santos are just some examples of relievers having disastrous 2012 seasons even without a change in role. Stuff happens to pitchers and it's not an excuse for stasis. Plus, Wilhelmsen's long hiatus from the game might make him the ideal candidate for such an experiment, as he has significantly less wear and tear on his arm than a typical twenty-eight year old.
Second, while Wilhelmsen is certainly a top-notch reliever, the Mariners are actually fairly well covered if they need to institute a new stopper. On the current roster alone, both Carter Capps and Stephen Pryor have the pure stuff to allow them to close in the big leagues. Both come armed with 100 MPH heaters and minor league closing experience. Capps in particular appears to have the skills for the job. A 2011 draft selection, Capps whiffed ninety-five hitters in under seventy minor league innings and multiple evaluators have suggested he has ninth inning upside.
But even if Pryor, Capps, or whoever ultimately becomes the closer isn't quite as effective as Wilhelmsen, the Mariners still stand to net value if Tom successfully translates to the rotation. Simply put, an average starting pitcher is much more valuable, in the aggregate, than a very good reliever. For example, in 2012 Wilhelmsen is fourth in the majors in innings pitched as a reliever, and his 1.4 WAR accumulated ranks sixth among bullpen arms. But what's gaudy for a reliever is pedestrian for a starter, as there are ninety-four starting pitchers who have accumulated at least 1.4 WAR so far in 2012, including luminaries like Joe Saunders, Luke Hochevar, and Kevin Millwood. Assuming the M's don't see a significant drop-off from a new closer, Wilhelmsen wouldn't even need to pitch all that well to make the move worthwhile for a team struggling to fill out the back of its rotation.
But if he did pitch well, the Mariners would stand to gain surplus value impossible to obtain from a reliever. While I'm not going to compare Wilhelmsen to C.J. Wilson, the lefty's success following the transition from reliever to starter does demonstrate the potential fruits of such a move. As a very good reliever in 2009, Wilson accumulated 2.2 WAR for the Rangers. After switching to the rotation prior to the 2010 season, Wilson compiled 10.5 WAR over the next two years, even as his velocity dipped and his peripherals dropped across the board. There is simply significantly more value to be had from a pitcher in the rotation than one in the bullpen, and even if Wilhelmsen doesn't approach Wilson's level of success, he could still pay long-term dividends for the club if he starts for multiple seasons.
This is something the Mariners have almost certainly discussed internally and it's a move that I'd be excited to see. A rebuilding team should be exhausting its options to upgrade the roster, and I believe that the chance to explore Wilhelmsen's value as a starter is of greater importance than letting him close for a mediocre ball club. There is too much potential benefit from a switch to not consider moving Wilhelmsen, especially considering the freshness of his arm, the ease at which the move could be made, and the strong internal options to replace him in his current role.
Again, this is all predicated on the third pitch. Ideally, Wilhelmsen continues to work on his change up out of the bullpen and in side sessions throughout the season. If the pitch stalls, then I can understand leaving him as a closer. But if it flourishes, this is a perfect opportunity to pick up value without spending a dime. Ultimately, I trust the Mariners front office to evaluate whether such a move would be in the best interests of the team. I would only be disappointed if it isn't explored at all.