Nathan (elbow) is working out at Chicago's Arizona complex, Patrick Mooney of CSNChicago reports.

EDGE Analysis

Nathan, who is returning from Tommy John surgery that forced him to miss the 2015 season, is still knee-deep into his rehab program. At 41 years old, age has to be considered a factor in whether he can return to big-league form again, but the veteran closer has had success in the majors as recently as 2014 when he saved 35 games for Detroit. Nathan working out in Arizona indicates that he's serious about making a major league return but that likely doesn't have a chance of happening until sometime after the All-Star break.