Is Rehabbing DL Hall Ready To Return To The Majors?

DL Hall's starts with Nashville have been intriguing as he's ramped up again from the second knee issue he had, and the Brewers' needs have changed over that span. They could have used some middle relief in May, but they've now brought back Jakob Junis and moved Bryse Wilson to the bullpen again, which gives real depth. So Hall's role is more likely to come back as a starter, and he's been stretched out in tandem with that, but has his stuff ticked up enough to get major league outs?

Is The Four Seam Fastball Back?
With the Brewers in April, Hall was averaging 92.3 mph on his fastball, a massive drop from his numbers out of the bullpen last year, where he was hitting the upper 90s with regularity. The move to a starting role likely meant some regression on the velocity front, but not one as large as this, and we can suspect now that the knee played a big part in this. Since rehabbing, it's ticked up to more of the range we saw in spring training, averaging 94.2 mph and passing 96 mph occasionally (he never reached above 94.6 mph in April). Because of his extension, this adds another tick to the velo, which affects hitters with a 95 mph average that can play in the majors.

With the movement profile, it's been a little more helter-skelter. The induced vertical break (IVB), which causes that rising effect, has remained where it was with the Brewers in April, which we expected to see tick up. He's getting around 200 rpm more spin on the ball, so I would have expected this to result in more rise, but that hasn't been the case thus far, and it's not entirely clear why. These spin rates are much closer aligned to where they were in 2023 (I think some breaking pitches also may have been misclassified in 2023 as no fastball should have 2900 RPMs):

The above are Hall's movement statistics on pitches in the strike zone. It is especially important to keep location constant when looking at VAA, and that's why I'm not entirely convinced by the heater just yet. That angle on the high fastballs is good, but with the added IVB he's capable of, it could be an elite pitch, and he could begin dismantling hitters with his four-seam. It should also be noted that Hall's success comes from a combination of factors rather than one elite point. The low arm slot, the big extension he gets off the mound, the IVB, the velocity, and some natural deception combine to explain his historical success behind the pitch, and that's difficult to quantify as a whole.

On a side note, he also seems to have switched his position on the mound slightly, which has changed his horizontal angle of approach to be more in line with his 2023 numbers. More spin-based movement could increase the disparity going forward, but I'd say this is a fairly benign change for now.

So, how have the results been? Well, his last start was his most promising despite featuring his lowest IVB on the fastball in a while. He generated a 23% whiff rate on his four seam (his previous three starts had rates of 10% and 7.1%) and a called strikes + whiffs rate of 42.9%. It gives a bit of hope that when he returns, that fastball will be a lot less hittable and that added velocity will be a big boost for him.

The Breaking Balls Are Located Poorly
The only other concern I have now is the curveball, which hasn't missed bats well this year. He has just a 7% swinging strike rate on what was a 60-grade pitch coming into the season, and it has nothing to do with how the pitch moves (we've had enough chat about that nerdy work today). Instead, he just hasn't been able to locate it at all.

If I told anyone where they'd like to throw their curveball most, it certainly wouldn't be in the upper and middle areas of the strike zone. Hall isn't getting it to dip in and around that lower edge of the zone, and it's hurting him a little this year. It was a 60-grade pitch because no one even recorded a hit against it last season, and they're still struggling this year, but he's not getting the swing and miss, which can hurt him when working ahead against hitters.

The slider is his other electric breaking ball, again rated 60/70 by Baseball America coming into the year, but the location has just been all wrong. From pinpoint precision in 2023 to leaving it up more often than not in 2024, especially during his rehab starts, I think the command is going to have to improve to get that whiff rate back from the 21% it's been in Triple-A to the 35% rate it had last season.

There is an element of concern over the damage that big league hitters can do against breaking balls in these locations, and it's something to keep an eye on. He may have focused a lot on the fastball regaining its qualities and has shown more durability and velocity overall on that front. Still, it won't matter if he's keeping sliders and curveballs up in the zone regularly. DL Hall is an incredibly talented fireballer, and it may not entirely click for him this season, but he has taken steps forward and can hopefully continue to do so after the all-star break.

What do you think of Hall's performances? Have they improved enough to restore some faith in him as a starter? Can he kick on like Garrett Crochet and Tanner Houck? Let us know your thoughts in the comments below!