Horton was removed from Friday's start against the Guardians in the second inning due to right forearm discomfort.
Horton's last pitch was clocked at 93.8 mph, which is about a two-mph dip from where he usually sits. The righty immediately called for the trainer after that offering before walking off the field and into the clubhouse. Horton yielded one walk over one-plus scoreless inning before being pulled. A stint on the injured list is a very real possibility, but the Cubs will send Horton for an MRI to determine the severity.