Nolan Arenado is in one of the worst slumps of his career

There are a lot of great things happening for the Rockies right now. Trevor Story is looking like a legitimate MVP candidate. German Márquez might be turning into an ace. Kyle Freeland finally got the cheat code for Coors Field. It’s September and the Rockies are in first place! But it is curious how they’ve gotten into first place. Or, more accurately, how they have gotten into first place without Nolan Arenado.

Look, I’m not trying to be a Debbie Downer or anything but after an 0-for-3 night on Wednesday Nolan’s season line dropped to .297/.379/.550 and an wRC+ of 130. I know what you’re thinking and you’re absolutely correct: that does look like a pretty spectacular year. In fact, those numbers would represent the highest OBP and wRC+ of his career and the second highest batting average. Sure, the slugging percentage is as low as it’s been since his sophomore campaign, but it’s not anything to worry about, right?

The concern with Nolan isn’t so much that he’s somehow having a bad year, but that he’s been a markedly different hitter in the second half. After a two homer game in which he went 3-for-5 in the first game back from the All-Star Break, Nolan was hitting .316/.398/.603 and had an wRC+ of 150. That was the high water mark of his season so far. He had a good-not-great .863 OPS over the following three weeks before being pulled from a game on August 10. He left due to an apparent shoulder injury that, we were told, only affected his throwing.

Arenado went from being 44% better than league average prior to August 10 to being 41% worse than average after it. That’s six extra base hits in the last month; he had that many between June 15 and 19. And anyone who has been watching can see it’s not the same Nolan up at the plate right now.

The slump is even more stark when you look at the rest of his career. FanGraphs keeps track of a stat called Weighted On Base Average (wOBA, click here to learn more), which is an all batting statistic that weights extra base hits higher than non-extra base hits and scaled to resemble an on-base percentage: around .300 is decent, around .400 is excellent. The chart below tracks Nolan’s 15-game rolling wOBA; every point on the graph represents Nolan’s offensive performance over the previous 15 games.

Source: FanGraphs

There are a lot of peaks and valleys on that chart because even the best hitters in baseball go through hot and cold stretches. What’s notable here is just how far Nolan has dropped off in 2018. While the decline has been less sharp than in previous slumps, it still represents the biggest drop-off since July 2015, when he posted a 51 wRC+.

So what’s going on? Comparing Nolan’s batted ball data pre- and post-injury a few things stand out. First of all, his BABIP went from .325 to .277 after posting a .320 in 2017. Digging a little deeper we find the likely culprit: Nolan is hitting more ground balls (37.7% to 50.7%), which are coming almost exclusively at the cost of his fly balls (39.5% to 26.9%), all while generating more soft contact (14.1% to 17.6%). When you hit fewer fly balls and more ground balls, and you’re hitting the ball less hard overall, extra base hits tend to dry up quickly and outs abound. That’s how you go from one of the best seasons in the league to one of the worst months of your career.

Fortunately for Arenado, he had quite the lofty perch from which to fall. But it’s still a worrying trend. While he hadn’t exactly maintained his blistering pace in the three weeks before being removed from that dramatic victory against the Dodgers, the correlation is pretty difficult to ignore.

At this point in the season everybody is hurt to some degree or another, so it wouldn’t be hard to imagine the shoulder is still bothering Nolan. Even if the shoulder is healed (or it really doesn’t affect his hitting), a day off may be in order to allow a mental reset. That’s hard to do when every game and every at bat matters so much for the Rockies push to the playoffs, but it’s to the point where manager Bud Black should consider whether a day off might help reset Nolan for the final push. After all, the last time Nolan got a full day off he went on to earn six extra base hits in five days.

Again, the news isn’t all bad. The Rockies managed to go 17-7 over the course of Arenado’s rough patch. And that might be the most encouraging part of all: the Rockies’ lost most of the production of an MVP candidate and still managed to launch into first place. The team is more than its star third baseman. If they can get him back right, they just might be able to run away with the franchise’s first ever division title.