Gregorius Is Hitting Again, But Will It Last?

On Monday night at Citizens Bank Park, Didi Gregorius stepped up to the plate in the bottom of the eighth. The Miami Marlins were leading the Philadelphia Phillies by a score of 2-1.

Rhys Hoskins stood at third base, 90 feet away from scoring the tying run, but there were two outs, and the Marlins had just brought in a tough southpaw reliever to face the Phillies’ left-handed shortstop.

Gregorius came through. He smacked the first pitch from Steven Okert down the right field line for a base hit, driving in the tying run. According to FanGraphs, it was the highest leverage at-bat Gregorius had taken all year, and he made it count.

With that hit, Gregorius raised his batting average to .313 and his OPS to .796. After Tuesday's game, those numbers are still quite respectable: .307 AVG and .786 OPS. He has had just 96 plate appearances—far too few to qualify for the batting title—but among NL shortstops with at least 75 PA, he ranks second in batting average and fourth in OPS.

His 119 wRC+ suggests he has hit 19% better than the average major leaguer, and 25% better than the average shortstop. He looks like his old self again.

Last season, there’s a very good chance Gregorius doesn’t get that game-tying hit. He batted .209 in 2021, with a .157 AVG against left-handers. His bat hurt the Phillies a lot more than it helped, as he finished with -1.82 Win Probability Added, worst for Philadelphia and third-worst among NL shortstops. As hard as it is to believe, he was somehow even worse in high-leverage situations, as demonstrated by a -0.43 Clutch score, per FanGraphs.

This year has been a whole other story. He is putting up career highs in batting average and on-base percentage. He has been an above-average hitter in most aspects of the game.

His resurgence has been a huge help to this team, especially since players like Nick Castellanos and J.T. Realmuto have not been hitting up to expectations. Gregorius has driven in and scored key runs on several occasions this year, and with Jean Segura out of the lineup for the foreseeable future, the Phillies will be counting on Gregorius to keep it up.

Can Gregorius Keep Up His Hot Streak?

As good as Gregorius has been, it’s too soon to say he has returned to his prime form. After missing time with a knee injury earlier in the year, he has only played 26 games and recorded just 96 plate appearances.

Two helpful metrics for judging if a player can maintain his offensive performance are BABIP and Statcast expected wOBA (xwOBA). Unfortunately for Gregorius, neither of these statistics look great for him—but that doesn't mean there's no room for optimism.

Batting Average on Balls In Play (BABIP)

Over the course of a full season, hitters can be expected to post a batting average on balls in play close to their career average. Therefore, if a hitter has a BABIP much higher than his career rate, there's a good chance he won't continue to hit so well going forward.

Gregorius has a .360 BABIP this year, compared to a .275 career number. This suggests he’s been hitting balls in advantageous locations and they have been dropping in for hits frequently, but it is highly unlikely he can keep it up.

If he were to have his career average BABIP this year, Gregorius would be hitting just .234 with a .288 on-base percentage. That’s a massive drop off from his actual production.

Those still aren't terrible numbers for a shortstop (the average shortstop is hitting .246), but because he has not been walking very much or hitting for any power, and because he is a poor defensive player, Gregorius really needs a high batting average in order to be a valuable contributor. If his average starts to slip, as his BABIP indicates it will, the rest of his numbers will quickly follow suit.

Thankfully, there are grounds for optimism. Gregorius might be able to maintain a higher-than-usual BABIP this year, because he seems to have modified his approach at the plate.

This season, just 31.1% of the balls Gregorius has put into play have been fly balls, compared to a 41.4% career average. Fly balls are the least likely type of batted ball to result in a hit, because they're so easy to catch, especially when a batter hits them as softly as Gregorius does.

By limiting fly balls and hitting more line drives and ground balls instead, Gregorius can hopefully sustain a higher BABIP, and therefore a higher batting average. He won't be able to keep up the .360 BABIP he has right now (that's just too high), but he can hopefully do better than his .275 career rate.

96 plate appearances does not provide enough data to know for sure that Gregorius has changed his approach (or that he can keep it up), but it stands to reason that a hitter who has never been a big power threat would adjust to the so-called "dead ball" by no longer trying to hit as many fly balls. It's a good strategy if he can make it work, and it's something to keep an eye on as the year continues.

Expected Weighted On-Base Average (xwOBA)

While the Phillies shortstop has a .344 wOBA this season, his xwOBA is just .311. For context, that's the difference between how Kyle Schwarber is hitting this year (.350 wOBA) and how Nick Castellanos is hitting this year (.317 wOBA).

While wOBA is based on the end results of plate appearances (single, double, out, etc.), xwOBA is determined by the quality of contact a player makes. Therefore, xwOBA shows that while Gregorius has gotten some good hits this year, he hasn’t been making very impressive contact.

Without making high quality contact, Gregorius will be hard-pressed to keep up a .344 wOBA all season.

In this case, the reason to be optimistic is that throughout his career, Gregorius has often been able to outperform his xwOBA. In his last three full healthy seasons (2017, 2018, 2020) Gregorius had a wOBA that was 30 to 40 ticks higher than his xwOBA.

This suggests Gregorius has certain skills at the plate that aren't properly measured by Statcast. That's a good sign, because it indicates he can continue to hit for above-average numbers despite below-average expected statistics.

However, while he should be able to outperform his xwOBA, he may not be able to do so to such a high degree this year. Because of the "dead ball," batted balls are not traveling as far as they used to. As a result, the league-wide xwOBA is much higher than the league-wide wOBA, which is not usually the case. That makes it much harder than usual for hitter to outperform his expected stats.

As counterintuitive as it sounds, we can no longer expect batters to hit like their expected wOBA—expected wOBA is just too high this year. A player who normally outhits his xwOBA by 30 to 40 ticks might only be able to outhit it by 15 to 20 ticks this season.

In a normal year, if Gregorius had an xwOBA of around .311, he might be able to maintain a wOBA close to .344, which is exactly what he did in 2018 and 2020. This year, however, that's a much harder task.

He can still outperform his expected statistics, but just like his batting average, Gregorius will eventually see his wOBA start to drop.

In Conclusion

Gregorius has been great for the Phillies so far this year, and his offensive production has helped make up for the inconsistent hitting of many of his teammates. Hopefully, as the season goes on, he will continue to contribute timely hits and RBI.

Going forward, however, Philadelphia must hope for better at-bats from the likes of Castellanos, Realmuto, and more. Gregorius is unlikely to keep hitting at his current pace, so he needs his teammates to step up and in his stead.

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