Re-exploring the idea of a six-man rotation

We are now just over two weeks away from Opening Day, and there is little clarity in the Cardinals' competition for the fifth starter spot. Going into Spring Training, the Cardinals openly talked about Carlos Martinez being the favorite to claim the last rotation spot, with Marco Gonzales being his primary competition. Jaime Garcia lurked as a wildcard who first had to prove himself healthy before he got consideration for the fifth starter spot.

Any time someone mentioned the possibility of having all of these pitchers healthy and ready for the beginning of the season, this notion would be dismissed with the old clichés: it's a good problem to have, you can never have too much pitching depth, and it will all work itself out by the beginning of the season. While a lot can happen in two weeks, the possibility of having everyone in the rotation healthy and ready to go by the beginning of the season is becoming more realistic every day.

So where does the competition stand at this point?

If you're looking at Spring Training stats (which may not have a lot of meaning), the gap between Martinez and Gonzales has perhaps tightened a little bit (at least as much as it can in the equivalent of less than two regular season starts). Furthermore, Jaime Garcia has complicated things a bit by showing good stuff (13 k's in 9 1/3 innings) and giving us hope that he has overcome his latest injury, thoracic outlet syndrome. If anything, there is less clarity in the 5th starter competition than there was at the beginning of Spring Training.

Which brings me to a topic that has been discussed on this site before: a six-man rotation. Back in January, Craig wrote a post where he discussed the possibility of a six-man rotation, and at the time, he dismissed it as a bad idea because it would take innings away from the team's best starters and give them to an extra, less talented starter. Things have certainly changed since January, though, to the point where Ben Humphrey and Aaron Schafer (aka the red baron) discussed the idea of a six-man rotation on the latest edition of the Viva el Birdos podcast. In this scenario, both Carlos Martinez and Jaime Garcia would both be in the rotation.

The reasons they provided in support of such a move are as follows:

• The Cardinals have a whole lot of pitchers who could be really good but have to prove themselves because of health (Wainwright, Wacha, Garcia) or a lack of major league exposure (Martinez, Gonzales).
• Jaime Garcia has a higher health-neutral floor for 2015 than Martinez and Gonzales. In addition, because of his recent injury history, Garcia may have a limited number of bullets, so to speak, so it might not make sense to buy time by sending him on a minor league rehab assignment.
• Carlos Martinez is at the point in his career where he has learned everything he has to learn at the Triple-A level and needs to be given a chance to start because of his enormous potential. Yo-yoing him between the bullpen and the rotation could further delay his potential development into a good major league starting pitcher.
• While he's had a good spring, Marco Gonzales still has room for development, especially with his curveball. The Cardinals can stash him at Triple-A and have him ready to step in the rotation this season if necessary.
• If one of the six starters gets injured, the Cardinals can simply shift back to a five-man rotation. Given the nature of pitching injuries, as well as the history of injuries in the Cardinals' rotation, there is almost a guarantee that one or more starters will be injured at some point this year. (Craig discussed this earlier in the week and concluded that there was just an 8.7% chance that the Cardinals' five starters made it through the season unscathed.)
• In the unlikely chance that the team makes it through the season with their six-man rotation intact, they will have succeeded in limiting the number of innings of all of their starters. The team has already stated that they want to limit the innings of Adam Wainwright, Michael Wacha, and Carlos Martinez (assuming he's in the rotation), and a six-man rotation would be one way to do it.

While I am personally intrigued by these arguments, I think it is helpful to look at the arguments against a six-man rotation to see if they apply in the Cardinals' situation. One of the most common arguments against a six-man rotation is that it will take innings away from a team's five best starters and give them to a sixth worse starter. For the Cardinals, a six-man rotation would theoretically take innings away from Adam Wainwright, Lance Lynn, John Lackey, Michael Wacha, and the fifth starter (Garcia or Martinez) and give innings to the other of Garcia or Martinez, depending on which pitcher would have lost out on the fifth starter's spot.

Here are the ZiPS projections for the starters that would make up this potential six-man rotation.

With the exception of Jaime Garcia, the Cardinals have five starters projected to have at least 2 WAR and a sub-4 ERA. Garcia's projection takes into account the likelihood that he misses a significant amount of time with an injury, as seen in his IP and zWAR numbers. If we assume that his rate projections (ERA and FIP) are reasonably accurate, regardless of whether he makes it through the season healthy or not, Garcia is clearly the weakest starter of the six. However, if Garcia is able to come closer to his career numbers (3.42 ERA, 3.50 FIP), an argument can be made that he can be as effective or nearly as effective (on a rate basis) as every Cardinals starter not named Adam Wainwright.

If the sixth starter is able to approximate the performance of the two through five starters on a rate basis, which very well may be the case with the Cardinals, then the main argument against a six-man rotation is severely weakened. Furthermore, the Cardinals are already trying to limit Adam Wainwright's innings as it is, so doing it in this manner may not be the worst idea.

The big question, of course, is how many innings Adam Wainwright would lose as a result of this arrangement. As Craig pointed out in his six-man rotation article, Adam Wainwright would end up with approximately 198 innings pitched if the team kept a six-man rotation for the entire season. This is a good deal off from the 244 innings Wainwright has averaged over the past three years, postseason included. However, this is assuming that no injuries occur and the six-man rotation stays in place the entire year. If the Cardinals only employ a six-man rotation for part of the season, they could still get well over 200 innings from Wainwright.

Perhaps the bigger concern would be the effect a six-man rotation would have on the bullpen. Having an extra pitcher in the starting rotation would likely mean having one less arm in the bullpen. The most likely bullpen arrangement would be having four right-handers (Rosenthal, Walden, Belisle, Maness) and two left-handers (Choate and Siegrist/Gonzales/Freeman). This would prevent the team from carrying Carlos Villanueva (a potential long man) or a third left-hander in the bullpen. Since Villanueva  (opt-out) and Freeman (out of options) would likely end up in other organizations if they don't make the team out of Spring Training, taking away a bullpen spot could directly lead to their exit from the organization.

With four off-days in the month of April, the most in any month besides July, the Cardinals could probably work with a six-man bullpen for a while. The team does have a stretch of 19 straight games, though, starting in late April. Having a six-man bullpen during this stretch would not be ideal, especially if Mike Matheny starts overusing closer Trevor Rosenthal. The team could choose to have one less player available off the bench, but this could create other a whole different set of problems, especially in extra inning games.

At this point, there is no evidence whatsoever to suggest that the Cardinals would consider going to a six-man rotation. In addition, the resulting bullpen/bench issues make it difficult to see this arrangement working out long-term. With that being said, I think that the Cardinals could make a six-man rotation work for part of the season. It would allow the team to get the most out of Carlos Martinez and Jaime Garcia, and it would help the team limit the innings of several important pitchers early in the year, ensuring that they aren't completely worn down by October. While there are reasons why no other team has employed a six-man rotation for an extended period of time before now, I think that the Cardinals' unique situation at least makes a six-man rotation something worth considering.