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A six-man rotation is a bad idea

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The Cardinals are looking to manage innings from their starters this season due to concerns with injuries, but a six-man rotation is not a good way to go for the Cardinals in 2015.

he doesn't need rest
he doesn't need rest
Kyle Terada-USA TODAY Sports

With Adam Wainwright coming off surgery, Michael Wacha with a rare shoulder condition, John Lackey 36 years old, and Carlos Martinez set to have an innings cap, the Cardinals are looking for ways to preserve innings for their starters. Derrick Goold reported on John Mozeliak's desire at Winter Warmup.

"You brought up two young pitchers [Martinez and Wacha] who we do have to manage how much they work," Cardinals general manager John Mozeliak said. "And I brought up Wainwright as someone who we want to be smart about. When you're making sure that the volume (of work) isn't too high, especially as you work your way to August and September."

With Jaime Garcia feeling great once again, there is the question of what to do if all the starters are healthy heading into the season. While the odds are long that the current projected starting five of Wainwright, Wacha, Lance Lynn, Lackey, and Martinez and a healthy and effective Garcia make it to April unscathed, a plan for that scenario has not been made public. After clearing the way for Martinez by trading Shelby Miller and refusing to sign or bring in another big-name pitcher, moving him back to the bullpen for a player with questionable health on the last year of his contract seems unlikely.

The topic of a six-man rotation has been broached. Fortunately, it does not appear to have much traction.

If the Cardinals are looking to preserve innings and remain effective as a staff, a six-man rotation is a terrible way to go. In theory, it makes some sense. Every pitcher gets an extra day off. They are better rested, stronger, and can pitch deeper into games. The number of innings they pitch overall is limited by the number of starts they make. The problem is that the innings that are taken away are the most effective innings for a starter.

Start with Adam Wainwright. He has been a workhorse, averaging 244 innings per year over the past three years, including postseason. He has been the Cardinals best starter, and going to a six-man rotation severely limits the number of innings he can pitch. Lowering the number some is a decent goal, but a six-man rotation takes away a huge chunk of the Cardinals' best pitched innings.

In a typical five-man rotation where the starts are divided evenly, each starter makes 32 starts. Setting a target for 200 innings, a pitcher who averages 6 1/3 innings per start ends up with 202 2/3 innings. Last season, Wainwright averaged a little over seven innings per start. Shifting just two outs per start to the bullpen saves more than 20 innings. Moving to a six-man rotation saves even more, but begins to create a huge gap that cannot be easily filled when a pitcher has been removed from the bullpen.

In a six-man rotation, every starter receives 27 starts. Setting a target again for 200 innings, if a pitcher averages 7 1/3 innings per start, he ends up with 198 innings. In order for a pitcher to hit 200 innings in a six-man rotation, he must, on average, get into the eighth inning every game. Every time he pitches just five innings, he has to complete two games to make up the difference. To get to 200 innings in a six-man rotation, the pitcher has to average more innings per start than Adam Wainwright did in 2014.

While the extra day's rest would in theory allow the pitcher to pitch better on the days he does pitch, that has not been the case for Wainwright. In 134 starts on normal rest, Wainwright has averaged 6.8 innings per start with a 2.98 ERA. In 60 starts with an extra day's rest, he has averaged 6.6 innings per start with a 3.21 ERA. Asking Adam Wainwright to go deep in games is one thing. Doing the same with John Lackey and Lance Lynn makes even less sense. Expecting Wacha, Martinez, and a sixth starter to pick up the slack with an innings cap, even split among three pitchers, seems like poor planning. If this approach is not feasible for Adam Wainwright, it is not going to work for anyone.

It might be reasonable to counter with a proposal allowing Wainwright, Lynn, and perhaps Lackey to go on every fifth day and then use an extra starter to get Wacha and Martinez more rest. However, adding the sixth man to the rotation takes an arm out of the bullpen, putting pressure back on Wainwright to take extra innings which is exactly the situation the sixth man is designed to avoid. Even without modification, the six-man rotation takes an arm out of the bullpen, putting more pressure on the starters to go deep into games. This situation is not just bad for the pitcher's arms, it is a bad strategy for preventing runs.

From Baseball-Reference, here are the league stats, grouped by innings in 2014.

INNINGS ERA BA OBP SLG
1-3 3.67 0.252 0.312 0.387
4-6 3.95 0.260 0.319 0.404
7-9 3.59 0.241 0.308 0.367

The first few innings pitched by the starter are his best. The middle innings, the starter tends to give a bit away, and the last few innings are either the bullpen or a starter who we already know is pitching well because he made it that deep into the game. Another starter adds innings when the starter is less likely to be effective in the best case scenario. Worst case, the bullpen has to cover more innings when it is already down a pitcher. This point is further illustrated by the performance of hitters the more times they see a pitcher in a game. Here are the times through the order numbers for baseball in 2014 against starters, again from Baseball-Reference.

PA BA OBP SLG
1st Time 43625 0.246 0.304 0.377
2nd Time 42836 0.256 0.313 0.395
3rd Time 32591 0.268 0.327 0.421
4th Time 3019 0.256 0.309 0.391

Plate appearances are included to demonstrate how rare it is that a pitcher gets to the fourth time through. There is survivor's bias as the only pitchers making that far are already pitching well and are likely to be removed at the first sign of trouble. Here is the same information in graph form.

times through the order

The stats take a noticeable jump with a 23 point jump in OBP from the 1st time to the 3rd time through the order and a 44 point jump in slugging for the same situation. Contrast that to relievers the first time through, who have a .241/.313/.366 slash line against their first time facing a hitter. Relief pitchers are not better than starters, but there is an advantage to being fresh and facing a hitter for the first time. There is a reason that starter ERA and FIP was 3.82 and 3.81, respectively in 2014 while the same numbers for relievers are 3.58 and 3.60. Starters who can pitch effectively the second and even the third time through the order and bridge the gap into the sixth or seventh inning are valuable because they get the game to the bullpen where the pitching team has an advantage. Innings from a starter are great, but moving around those innings so more come late in games as opposed to the beginning gives the team no advantage.

Managing innings for the rotation is a good goal, but giving starters extra rest and removing an arm from the bullpen hurts the team more than it helps. The team can let Wainwright go seven innings on most days and not suffer for it as long as he gets taken out after six a few times here and there. There are going to be days when Wacha and Martinez should leave the game after just five innings to preserve their innings. Increasing pressure on the bullpen might not seem ideal, but a modified six-man rotation does not help the problem unless the arms are being shuttled back and forth between Memphis. Using the minors could work for that sixth starter on occasion, but at that point the gains are questionable.

The tact the Cardinals should take if it truly wants to preserve innings for the starters is to employ a trusted swingman who can go more than one inning. Using a majority of the bullpen to navigate innings six through nine is a good way to wear out a bullpen. However, using one pitcher for 2-3 innings every three or four games takes pressure off of the rest of the bullpen, does not overly tax the starters and bridges the innings gap the Cardinals could find themselves in. Based on postseason usage, Marco Gonzales appears ticketed for a high-leverage role in the bullpen, but the Cardinals do have some minor league starters in Tyler Lyons and Tim Cooney who could slot into the bullpen in a long relief role.

The long reliever does not have to be a pitcher who just gets outs and saves the bullpen in blowouts. That pitcher can get important outs in the middle of the game. There needs to be trust between the manager and the reliever as well as between the manager and the rotation, but keeping the rotation healthy and the bullpen rested while winning games is the ideal scenario for the Cardinals. A six-man rotation accomplishes little in that regard. A true swingman could be just what the Cardinals need in 2015.