Prior to the 2025 season, one of my bold predictions was that DJ Herz was poised to have a breakout season. Back in 2024, Herz showed swing and miss stuff, while throwing more strikes than expected. However, after a rough Spring Training, it was revealed that Herz had to undergo Tommy John Surgery.
Since then, the left hander has faded out of the picture and has become a forgotten piece of the Nats future. That is going to change really quickly though because Herz is back on the mound. This afternoon
the 25 year old lefty made his first rehab start in Rookie Ball. Herz overwhelmed the FCL hitters he faced, throwing two perfect inning with four strikeouts.
Outside of just getting back on the mound, the most important thing out of this outing is that Herz did not walk anybody. In his minor league career, Herz had serious control problems. He has walked 5.88 batters per 9 innings in his MILB career. However, that did not stop him from being a successful pitcher because his stuff is so good.
In case you forgot, Herz has a dynamic arsenal. His fastball averaged 93.5 MPH but it plays way above the velocity. This is due to his deceptive delivery, his big extension down the mound and the elite shape of his fastball. In 2024, the whiff rate on his fastball was over 30%, which is bonkers for a heater that is only in the low to mid 90’s.
However, he was not known for his fastball in the minors. As Herz rose through the ranks, scouts buzzed about his changeup. The pitch has 10 MPH of velocity separation from his fastball and has great downward movement. It looks like the fastball most of the way before falling off the table.
That changeup got good results, but did not play like an elite pitch. Sometimes Herz would slow down his arm when throwing the changeup, which tips off the hitters. When he sells the pitch well, the changeup can be devastating. Herz’s third pitch is a slider which is not a special pitch on paper, but plays well off of the fastball and changeup.
When DJ Herz had his best stuff, he was absolutely electric to watch. There was an outing against the Marlins in 2024 where he struck out 13 and walked nobody. I think it was the most dominant outing from a Nats pitcher since Max Scherzer left DC. He had the Marlins hitters on a string.
The flashes of elite stuff is what made me so excited about Herz entering 2025. It also made his injury such a bummer. He has been out of the picture for nearly a year and a half now. However, now that he has started a rehab assignment, that puts the Nats on the clock. Pitchers rehab assignments can only be 30 days long. After the 30 days, the team will have to make a decision to either call Herz up to the big leagues or send him to AAA for more reps.
If Herz continues throwing the ball like he did today, that will become an interesting decision. At worst, I think Herz could be electric in that multi-inning relief role that Brad Lord and Mitchell Parker have been in. Herz would be an immediate upgrade over Parker in that role.
With Herz coming back from a serious injury, I do not think the Nats will throw him right back in the rotation. He will probably be eased in either in the minors or the bullpen. This is the first step of his rehab assignment, and we will see what is next. I would assume his next rehab start will either be in Low-A or High-A, unless the Nats like having him in the confines of West Palm Beach. Herz should steadily throw more pitches as he builds up, and will eventually face tougher competition.
This is something Nationals fans should be really excited about. If Herz can keep his walk rate in the 9-10% range that it was in 2024, he will be a piece of the Nats rotation moving forward. His 27.7% strikeout rate when we last saw him in the big leagues was elite, and would give this Nats pitching staff a new element. Herz can blow fastballs by hitters in a way most of these Nationals pitchers cannot.
As he continues his rehab assignment, I will be watching the walk numbers and the velocity once it is available. Those are the two things that will tell you how close Herz is. We did not see the velocity today, but Herz not walking anybody is a very encouraging sign. It shows that he is already feeling sharp, which is awesome to see in his first time back in game action.
The Nats pitching this season has not been great, but there is help on the way. Between Herz, Jarlin Susana and Travis Sykora, there are a lot of young arms on the mend right now. Herz will be the first to make an impact, and if he is at his best, that impact could be loud.
