In 2016, the Cubs went all the way to early July — 83 games — before they started anyone other than their five regular rotation starters. Adam Warren started Game 84 (you forgot about that, right?). Then they went another 20 games, to Game 104 before a “sixth starter” was on the mound to begin the game.
That one worked out all right, even though the starter got pounded. (Incidentally, that starter recently signed a minor-league deal with the Diamondbacks, so we might see him throw against the Cubs in spring training.)
Later in the summer, in order to give starters rest for the postseason, Joe Maddon gave Mike Montgomery five starts and one each to Jake Buchanan and Rob Zastryzny.
Now, it’s been reported that the Cubs could consider a six-man rotation:
The Cubs haven’t officially mentioned the possibility of a six-man rotation yet, but there have been hints, and the signs are there:
• Cubs manager Joe Maddon is a proponent of the six-man rotation, having used one at the end of the 2016 regular season and suggesting that more teams could do the same at the end of their seasons to mitigate workload.
• Epstein thinks about starting pitching staffs as eight, nine, or 10-man units. No team is better prepared to go to a deeper rotation than Chicago.
These are valid points and they took on more meaning when the Cubs signed Brett Anderson, who (if healthy) should make the rotation. What that would do to Montgomery, who was basically tagged as the fifth starter after Jason Hammel’s departure, is uncertain.
In modern baseball, where every starter pretty much goes all-out from the first pitch knowing he’ll be relieved (often) after seven innings, getting starters rest is important. In NPB in Japan, where teams play six-day weeks and have every Monday off, starters go once a week. In 2014, Yu Darvish made this exact point to the New York Times:
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.
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.”
Two weeks after that article was published, Darvish left a game early and didn’t pitch again until 2016, after Tommy John surgery.
In some ways, going to a six-man rotation is counterintuitive. In a five-man rotation, each starter (theoretically) gets 34 starts. What a six-man rotation suggests is that you would take five or so starts away from your five best starters and give them to the sixth-best guy. That doesn’t sound optimal, unless you have accumulated enough depth in the rotation to do that, and that’s something Theo & Co. have tried to do. It also means you’re going to have a seven-man bullpen instead of eight if you do it all year... unless you have a 14-man pitching staff, which isn’t optimal either.
So what you’d probably want to do is a “modified” six-man rotation, where, like the Cubs did in 2016, you don’t really use it until later in the season. Here’s a hint that’s what the Cubs might do:
Joe Maddon will likely shy away from 6-man pitching rotation in April because of open dates, but he's certainly open to it later in season.— 670 The Score (@670TheScore) February 14, 2017
That seems right. In fact, I’d argue that with five off days in April, the Cubs could actually use a four-man rotation and still give starters normal rest, perhaps slotting the fifth guy in when needed.
It’s in June (one off day), August (two off days) and September (two off days) when this sixth starter would be useful. That guy (maybe it’s Montgomery, maybe it’s someone else) would do bullpen work the rest of the time. This is what people used to call a “swingman,” someone who could switch back and forth between bullpen and rotation. Terry Mulholland is probably the most recent example of a guy who did that, and did it well. A rotation starter early in his career, over his last nine seasons (1998-2006) he made 382 appearances, 307 in relief and 75 starts. Jim Slaton is another guy who did this well for a few years near the end of his career, in particular for the 1982 A.L. champion Brewers.
Personally, I think Maddon will likely do what he did last year -- later in the season, when he wants his starters rested for the postseason, he’ll slot in someone as a “sixth” starter from time to time. He had that luxury in 2016 in part because the Cubs had such a big division lead. If that’s not the case this year, he might not do it. Maddon’s not the kind of manager who sets something in stone and never changes; he always will try to adapt to the situation.
So we could see a six-man Cubs rotation this year, but only if the circumstances for it are right.