Major League Baseball has been suffering an epidemic of Tommy John surgeries, some made on pitchers who haven't thrown one big-league pitch; other pitchers have undergone multiple TJ procedures.
Darvish said he believed that a shift to a six-man rotation by major league teams could significantly reduce the stress on all those elbow ligaments by giving pitchers a critical extra day to rest and limiting their starts. Darvish outlined his thoughts on the subject to Japanese news media outlets during the All-Star Game in Minneapolis last week, but he declined to expand on it further on Monday. "I know if you have six starters, there are going to be other problems that it entails," Darvish said. The issues include expanding rosters to accommodate another starter, and resistance from other pitchers who prefer to pitch every fifth game as part of a five-man rotation. Speaking to Japanese reporters in Minneapolis last week, he said, "If you really want to protect players, we should add one more spot to the starting rotation."
The New York Times article linked goes on to discuss how NPB teams have every Monday off and thus can go with a six-man rotation with everyone starting once a week. It appears to limit the wear and tear on pitchers' arms:
"I loved pitching once a week," said Colby Lewis, a Rangers pitcher who played for the Hiroshima Toyo Carp in 2008 and 2009. "You always felt great, really healthy and strong. Then you come here and pitch every fifth day, and it’s different. Look what happened to Tanaka. I’m not saying that’s the specific reason he got hurt, but it’s worth thinking about."
Lewis went 26-17 with a 2.82 earned run average in his two years in Japan and made 54 starts.
(Yes, I know Colby Lewis made some dumb comments recently about being bunted on when his team had a defensive shift. This isn't about that, it's about Lewis' experience in Japan, which is relevant to this topic.)
Having a six-man rotation might mean that you could still have a 12-man pitching staff. Darvish indicated in the article that it isn't the number of innings thrown, but the days off in between starts, that reduces the wear on a pitcher's arm. Thus pitchers in a six-man rotation could probably throw the same number of innings they do now, maybe going seven on a regular basis instead of six. A six-man rotation would result in every rotation starter for a team making 27 starts a year instead of 33 or 34, but still possibly throwing 180 to 190 innings, with the top starters still throwing about 200. If it reduces injuries as Darvish thinks it would, you'd need fewer injury-replacement starters hanging around Triple-A.
Of course, this means that teams would have to find more qualified starters -- 30 more of them, one per team. Are there enough qualified minor leaguers around, or guys who have been waived or released because they couldn't make five-man rotations, to fill six-man rotations? Or are there relievers around who might be able to be stretched out to fill these slots?
What do you think? Vote in the poll and weigh in, in the comments.