Later today, 21-year-old right-hander Deivi García will make his playoff debut in Game Two of the ALDS. The Yankees announced as much yesterday, when they made the surprising decision to push Masahiro Tanaka back to Game Three against the Rays. The Yankees have shown confidence in García, but the move likely has more to do with Tanaka that it does the former top prospect.
As Tyler mentioned in his writeup of the news, the main reason for pushing Tanaka back one day likely is to give the veteran a bit of extra rest. Tanaka has made the majority of his starts as a Yankee with more than four days rest, perhaps because in Japan, where Tanaka pitched in NPB for seven years, most teams deploy a six-man rotation that gives starters five or six days of rest. Starting him in Game Three would give Tanaka six days between starts.
This seems like the simplest explanation, though I want to look at it a bit more closely to see if it holds up. Does Tanaka perform better on extra rest, giving the Yankees clear reason to push him back? It’s a straightforward exercise to bring up Tanaka’s splits on his Baseball-Reference page, and dig into how he’s performed on different amounts of rest.
At the top level, the idea holds up to scrutiny. On four days rest, Tanaka has allowed a .728 OPS for his career in 56 starts. He’s allowed a .716 OPS in 86 starts on five days rest, and a sterling .628 OPS in 31 starts with six days of rest or more. Tanaka’s ERA on five days rest is just a tad higher, at 3.82, than his 3.75 figure on four days rest, but he’s put together a 3.50 ERA on six-plus days. His walk rate has stayed level across levels of rest, but his strikeout rate has increased with every extra day of rest, while he allows hits at a lower rate with more rest. His lowest home-run rate has come with six-plus days rest.
However you splice the surface-level numbers, Tanaka has performed better with five days rest than four, and better on six-plus days rest than five. Of course, while those figures tell us an obvious story about how Tanaka has played better, they don’t give us an exact picture of why he’s played better. As it turns out, pinning down the why of Tanaka’s superior performance is trickier than just teasing out the fact that it exists.
The best tactic I could come up with was to scan through Tanaka’s game logs on Brooks Baseball, to see if he experienced velocity jumps on extra rest. If Tanaka saw his velo spike with more rest, we could view that as a proxy for better stuff with more rest. Yet going through Tanaka’s starts over the past three seasons, not once has Tanaka made a start on six-plus days rest and recorded an average four-seam velocity higher than his average velocity on that season. Not once! Every time Tanaka has gotten extra rest since 2018, he’s thrown slower than is typical.
For a specific example, we only have to look back to last week, when Tanaka started on six days rest in Cleveland in the Wild Card round. Tanaka averaged 92.1 mph on his fastball, compared to his season average of 92.5 mph. Maybe that had something to do with the bad weather that night, but it’s telling that on extra rest and with playoff adrenaline pumping, Tanaka didn’t pump extra heat.
Better stuff doesn’t look like an explanation for Tanaka’s improved work on extra rest, and unfortunately, there’s no easy way that I’ve seen to use Statcast to splice out Tanaka’s starts based on rest to gain further insight. Based on the fact that he hasn’t shown better velocity, and that he has still allowed fewer hits and struck out more batters with extra rest, we can hypothesize that Tanaka’s command is sharper with extra rest, helping to induce more whiffs and less hard contact with the same raw stuff.
I find the extra rest reasoning compelling, but there are certainly other reasons the Yankees may have seen fit to move up García. Our John Griffin posited in PSA Slack that starting García early opens up the possibility of using him out of the bullpen on his throw day in Game Five, a job probably better suited to García’s young arm. I also theorized the Yankees may simply view García as one of their three best starters, but felt wary of having the youngster make his playoff debut in a Game Three that could have been a must-win game or a putaway game, and instead reserved that task for the veteran Tanaka.
Whatever the reason, I can think of one point against the strategy; this trick can only be pulled once. The lack of off-days, as well as the lone off-day between the ALDS and ALCS, means that pitching Tanaka in Game Three lines him up for Games Two and Seven of the ALCS on just four days rest. The Yankees won’t be able to get Tanaka any extra rest next round unless they sweep. They also won’t be able to start Tanaka in Game One of the ALCS, should they advance but burn Gerrit Cole on short rest later in the series.
It’s anathema to discuss future series before winning the current one, but the Yankees’ decision-makers must be forward-looking, even if their players are singularly focused on the game in front of them. Either way, the small decision to push Tanaka back does come with a bit of hidden complexity. The numbers back it up, at least in terms of boosting their odds of an effective Tanaka, but it could have farther-reaching effects down the road. In any event, let’s hope that Tanaka’s Game Three outing comes in a win-and-advance situation. A sweep of Tampa would make long-term strategic thinking a whole lot easier.