Horton averaged 93.4 mph (touched 94.9 mph) with his fastball in his first start for Triple-A Iowa on May 4 and averaged 93.9 mph (touched 95.5 mph) in his second start May 10 after sitting at 95-97 mph with his fastball and regularly touching 98 mph in 2023.
This doesn't necessarily mean Horton is dealing with anything physically, but it's worth noting that he's not working with the same caliber stuff as was advertised during the offseason. Horton had a 1.10 ERA, 0.92 WHIP and an 18:2 K:BB in 16.1 innings across four starts in a return assignment to Double-A Tennessee before getting promoted to Triple-A at the end of April. He has given up eight earned runs on seven hits, eight walks and two home runs while striking out 11 in seven innings through his first two starts at the highest level of the minors. Since Triple-A pitch velocities are public, it's worth keeping tabs on Horton's pitch velocities over his next few outings to see if things keep trending up. This is also Horton's first experience with the automated balls and strikes system at Triple-A, so perhaps that's partly to blame for his elevated walk rate.