What You Need To Know About Relief Prospect Hayden Harris

This might be Atlanta's most anticipated relief prospect debut since AJ Minter in 2017

Finally, the Braves have called up prospect Hayden Harris to the majors.

An undrafted free agent out of Georgia Southern, Harris has been one of the best pitchers in all of the minor leagues, allowing just three earned runs on the year. His performances have resulted in a furor for his call-up, making this the most anticipated relief prospect debut for Atlanta since AJ Minter started unleashing cutters in 2017.

Who is Hayden Harris, how did he get to the Braves, and what should we expect from him in the majors? Let’s talk about it.

Who is Hayden Harris?

BIO: 6-0, 186 pounds. Born March 2nd, 1999 in Augusta, GA

After a five-year career at Georgia Southern, one where he went 8-7 with a 5.30 ERA almost entirely as a reliever (95 appearances, 8 career starts), there wasn’t a lot of MLB interest in taking Harris that summer in the draft.

And by ‘a lot’, I really mean ‘any’. He went undrafted.

Harris joined a summer ball team, spent some time with the Savannah Bananas (back before Banana Ball was the full-fledged phenomenon it is now - it was a thing but not a THING), and eventually connected with a Braves scout on LinkedIn. Seriously.

Back in early October 2023, I interviewed Harris for a segment of my podcast Locked On MLB Prospects. We discussed his journey from college to getting signed by the Braves, shooting through the system in one season, and how he was in Truist Park helping the Braves prepare for the NLDS against Philadelphia.

Here’s a timestamped link to the interview:

Who has he been in Atlanta’s minor leagues?

One of their best relievers this year, that’s all. He wasn’t always this good, though.

As I mentioned earlier, he pitched for three levels of Atlanta’s system (A-A+-AA) in 2023 and went from Double-A to Triple-A in 2024.

He wasn’t always good in those stints, though, most notably putting up a 7.36 ERA in 22 innings for Gwinnett in 2024 and then struggling in the Arizona Fall League after the season.

But he righted the ship this year, starting off in Double-A Columbus and dominating. After allowing just two earned runs in his 22.2 innings for the Clingstones, he bumped up to the Stripers in early June. All he did for Gwinnett was pitch 25.1 innings with a grand total of one earned run allowed, coming on July 8th versus Indianapolis on the road when Pirates prospect Liover Peguero turned on an inside sweeper and got him on a homer to left field.

25.1 innings with one run is an ERA of 0.36. See why people were clamoring for him to get a call-up?

It’s not like this was luck on the part of Harris, though. In those 25.1 innings, he allowed just eight hits and nine walks while striking out 36. He also hit four batters, so 21 baserunners in total. When you face 93 batters and less than one-fourth of them even reach base, that’s pretty good.

What does he do that’s special?

He has a low velo four-seam fastball that’s virtually unhittable, that’s what. I remember sitting outside the Braves spring training clubhouse in 2024, talking with Justin Toscano and Mark Bowman about how his velo’s nothing impressive - He averages just 91.5 mph this season on his tracked four-seamers¹ - and yet nobody seems to be able to hit the fastball.

Opponents are hitting just .111 with a .167 slug off his heater. Let’s talk about how he does it.

It’s because of the Vertical Approach Angle.

Referred to as VAA, it’s the angle the ball takes as it travels downward to the plate. Remember, pitchers are up on a mound throwing down to the plate, which is on flat ground, so they’re always throwing downhill and almost² every pitch crosses the plate lower than where it was released. It’s essentially the inverse of launch angle, which is the angle a batted ball takes after contact.

For VAA, the flatter the angle, the more ‘straight’ the ball’s flight appears to the hitter. If you’re thinking that this is a similar concept to the Induced Vertical Break of Spencer Strider’s four-seam fastball, think of VAA as a function of where you release the pitch and IVB as a function of how much you backspin the pitch. And no, most guys don’t have outlier numbers in both areas - it’s usually one or the other.

Vertical release point and extension (how far in front of the mound you release the ball) together account for about 95% of where a pitcher’s VAA ends up. (Shoutout to the managers of the University of Iowa baseball team for their work on this).

Ethan Moore, who now works in R&D for the Minnesota Twins, did some semi-public work on how this interacts with specific pitches a few years ago. (Here’s a link to the public part of the work over at Prospects365.) To break it down, fastballs with flatter VAAs work better up in the zone (where you like to throw a four-seamer), while fastballs down in the zone do better when you have a steeper VAA (like a sinker/two-seamer).

(Interstingly, two of the standout pitchers who use low VAA fastballs to great effect are Bailey Ober and Joe Ryan, both members of the Twins. See why they hired Ethan?)

But that’s not the only thing that Harris throws.

He’s mostly a three-pitch guy - fastball, sweeper, and a splitter. It’s fastball dominant, sure, using that at 69.2%, but he throws 23.3% sweeper and excels with landing it to both sides of the plate. It’s also hard for opponents to hit, with a .056 average and .222 slug off it. He also uses a splitter about 4.7% of the time and it’s yet to give up a hit, although we’re talking about a sample size of 19 thrown on the season. He also has a trio of other options that he’s used a combined ten times in a curveball (six), slider (three) and changeup (once).

All three pitches miss bats well. The fastball and splitter both have whiff rates of about 28%, while the sweeper’s currently at 52.2% whiffs. He’s given up a combined four barrels all season in 402 pitches thrown, two each on the fastball and sweeper.

What to expect from him in the majors

I genuinely don’t know. It’s hard for me to automatically say he’ll be this dominant against major league hitters, because who would be, but it’s also hard for me to say he’s going to completely fall on his face. I think he’ll be fine, which is really the most important thing.

I also don’t expect him to have any workload concerns, as he’s pitched just 48 innings this year and he went 50 and 59 innings the last two seasons. It’d be different if this were a playoff team, but we all know it’s not, so let him eat out of the pen for the rest of the year.

I’m incredibly excited to see what he can do.

1. Triple-A is part of Statcast, but Double-A is not, so this is a 280 pitch sample.

2. Unless you’re Tyler Rogers, a submariner who has the lowest release point in baseball by nearly a full foot