Horton (elbow) underwent Tommy John surgery Thursday and is expected to be sidelined up to 16 months, Taylor McGregor of Marquee Sports Network reports.
Horton required a full Tommy John repair on his right UCL, which means he's unlikely to be ready to pitch again for the Cubs until the second half of 2027. The 24-year-old has authored a 2.66 ERA in his first 25 appearances (24 starts) at the major-league level.