Horton was removed Wednesday from his start with Triple-A Iowa due to right lat soreness, Maddie Lee of the Chicago Sun-Times reports.
Horton allowed two runs and recorded just three outs Wednesday before being lifted. The right-hander has been sent to Chicago to be examined. Horton has offered a mixed bag of results since being promoted to Iowa earlier this month, striking out 22 over 18 innings but also walking 11 and giving up 15 runs. Between the uneven recent results and the injury, it's unlikely the top prospect will be seen in the big leagues anytime soon.