Mejia joined the White Sox's 60-man player pool Tuesday, James Fegan of The Athletic reports.
Mejia will be part of the group of 16 players working out at the team's secondary camp, meaning he's unlikely to be one of the first names called on in the event of an injury crisis. He's received big-league time in each of the last four seasons but hasn't stood out, posting a career 4.62 ERA in 154 innings and a 6.61 mark in 31.1 frames last year.