It was almost a year ago that Jordy Mercer played his first game of the 2014 season at shortstop. Mercer came up in early May to play second base with Neil Walker on the disabled list. Walker returned on May 13th, and Mercer started his first game of the season at shortstop on May 15th. A few weeks later, Mercer was named the primary starter, which was a relief to Pirates fans who were tired of seeing Clint Barmes’ bat in the lineup.
When it comes to the shortstop position, defense has a ton of value, and is highly underrated. That’s especially true for a team like the Pirates, who have had the highest ground ball rate in baseball the last two years. Barmes has been one of the best defensive shortstops in the league, but has no offensive value. That overall package still has value, especially to a team that gets a 50% ground ball ratio. But that doesn’t mean you need to have a defense-only shortstop.
The Pirates made the switch to Mercer, sacrificing some defense in exchange for much better offense. Barmes had a .558 OPS last year. Mercer had a .772 OPS. Barmes was much better than Mercer defensively, but Mercer was much better than Barmes offensively. Overall, Mercer’s increase in offense trumped Barmes’ increase in defense. That led to a 1.4 WAR from Mercer, compared to an 0.6 WAR from Barmes in almost the same amount of playing time.
The hope coming into this season was that Mercer could improve his defense, which is something he was working on with Barmes during spring training. So far, Mercer has improved his defense. He went from a -9.4 UZR/150 last year to a 5.3 UZR/150 this year. One disclaimer about UZR is that you need to factor in sample sizes.
When it comes to explaining sample sizes, I compare UZR to batting average. If a guy hits .300 in a month, you wouldn’t call him a .300 hitter. If he hits .300 in a year, you wouldn’t call him a .300 hitter, but he would be closer to that label. You’d only call a guy a .300 hitter if he does this consistently over several years. It’s the same with defensive ratings and UZR. Mercer was bad defensively last year, and has been good in about a month and a half this year. Neither of those are good enough to make a grand conclusion.
That said, it is good to see Mercer starting off so well defensively. The downside is that his offense has really taken a hit. Mercer has a .545 OPS this year, meaning that so far he has been Clint Barmes offensively, and Clint Barmes-lite defensively. He has been hitting well lately, going 9-for-23 with three doubles and a homer since the start of the Cardinals series last week. But that’s a sample size of six games, and all you can do is hope that’s the spark he needs to turn things around.
Looking at the advanced metrics, there are signs that Mercer will turn things around. He has a BABIP of .242, which is well below his .330 last year, and his .300 career BABIP. In the minors, he mostly stuck in the .300 range, and was never as low as .242. I don’t expect this to continue.
Likewise, his power is way down, with an .082 ISO. He had a .150 ISO last year, and he had a career .132 ISO in the minors. A big factor here is his HR/FB ratio, which is at 3.6%. Mercer was at 9.9% last year, which is a normal range. A normal range this year would have given him about two more home runs on the season. His line drive rate is also down, at around 10.9%, compared to 22.8% last year. The downside is that this has been replaced with ground balls, with his ground ball rate going up to 58.7%, from 46.8%.
This is all very similar to the trends that Neil Walker and Pedro Alvarez were displaying at the end of April. They both had low BABIP, HR/FB, and line drive ratios. Since that point, both have gotten back to normal.
When I wrote about Walker, I pointed out that if his BABIP numbers regressed to the mean, then he’d be putting up a .314/.360/.510 line going forward. His line since that article? .321/.438/.509. I actually wrote that I thought Walker would end up below the line I calculated, but he has been above that line so far. I still think don’t think he’s capable of these monster numbers going forward, but I do think he could post an OPS above .800.
Likewise, Alvarez had a .667 OPS at the time, and I said he should have an .828 OPS going forward — and possibly higher — if his BABIP were to regress to the mean. Since that point, he has had a .777 OPS, which isn’t great, but is much better than what he was going previously.
Due to the limited amount of playing time in his pro career, I’m not sure I could come up with a similar analysis for Mercer that wouldn’t end up with “he’s probably going to return to last year’s numbers”. I do think the BABIP and HR/FB ratios are low, and I think they will be closer to last year’s numbers than this year. To be fair, we couldn’t also say that Mercer’s defensive improvements will stick around, while dismissing this year’s offensive struggles. The hope would be that Mercer’s offense indicates some bad luck, while the defense indicates that his work with Barmes during the off-season is paying off.