When a 31 year-old reliever signs a minor league deal, and then does not make the team out of spring training, you generally expect that their career is mostly over. Mike Mayers has turned that situation into an opportunity over the past two outings as “the bulk man”, throwing 10 2⁄3 innings while giving up only one run. So, has the veteran found something the Royals can count on, or is this just a lucky couple of games?
I will start with the bad news, but I promise there is some reason for optimism with Mayers. You and I already know that he is not actually going to post a 1.35 ERA and contend for a Cy Young this season, so there is definitely some regression coming. His FIP, xFIP, and xERA all agree that his performance so far would typically give you an ERA somewhere in the threes, which for a Royals starter in 2023 would be AMAZING!! Any sub-4 ERA sounds great right now with only two other starters being below 4 right now, and one of them is hurt while the other has only started one game. Technically, Mayers has not started a game yet, but if there is an opener into him going five to six innings, that makes him in effect the fifth starter.
The reasons he cannot keep being as good as he has been so far are pretty simple. He has had some BABIP luck and his strand rate is 95.6%, which is very unsustainable. The highest strand rate last year for a qualified starter was Julio Urias at 86.6%, and no one has ever mistaken Mike Mayers for Urias. Some of those base runners are going to start scoring, and that number is going to fall at least 10 to 20%.
An even bigger reason for not expecting Mayers to continue is his stuff. Stuff+ factors things like release point, velocity, vertical and horizontal movement, and spin rate to measure the physical characteristics of a pitch and its quality. According to Stuff+, Mayers is at 94, roughly half a standard deviation below league-average. Last year he was at 98, but he was in a reliever role, so the drop is to be expected. The difference is that while his pure stuff is worse, his Location+ and Pitching+ have both been above-average, much better than last season. Overall, his stuff is not good enough to be an elite starter or reliever, but if he can pitch better with improved location, at least some of the improvement may be sustainable.
One more statistic jumped out as to why he will come back to earth, and that is a HR/FB rate of 8.3%. His career rate has been 14.9% and he has allowed 1.59 HR/9, but this season he has given up just one homer in 13 1⁄3 innings. In the shortened 2020 season he did have a 0.60 HR/9 rate, but that was a very small 30 inning sample, so there is no reason to expect he can actually avoid the long-ball like this, though I do expect him to give up fewer home runs this season because of one big change to Mayers’ game, and that is the addition of a sinker.
He did throw a sinker last season according to Baseball Savant, but he only threw it nine times (1%), and he has thrown it 13% of the time this year. Throwing a good sinker would typically increase a pitcher’s ground ball rate, and for Mayers that has definitely been the case. His career rate has been 37.4% with the last two years being almost exactly that. This season, he has spiked that rate to 45.5%, which should keep some number of balls from leaving the yard and hopefully increase double plays as well.
If you are being charitable, the Royals rotation right now could be characterized as thin. Mike Mayers has been good enough the first two times out that the Royals have to keep running him out there in this role. With or without the opener is up to them, though they might consider using the opener in front of Lyles who is definitely the weakest link. He cannot sustain what he has done thus far, but could he be a competent back end of the rotation starter? I think he might. As long as you are expecting a 4ish ERA over an average of 5 to 6 innings. There is also a chance he reverts back to last year and ends up off this team in a few months though, so some optimism is due, but not too much.