MILWAUKEE — Yu Darvish’s rehabilitation from right triceps tendinitis has advanced to the stage where he’s scheduled to pitch off a mound Tuesday at Miller Park for the first time since pitching in a game May 20.

The Cubs might not have a finish line for Darvish’s rehab, but his bullpen session could help shape a realistic target date for his return to the rotation.

“We’ll see how well it goes, how it feels,” manager Joe Maddon said. “The next day is what really matters.”

Because of the long layoff, the Cubs will continue to be deliberate in monitoring Darvish’s recovery. Darvish didn’t throw for nearly 10 days after he was scratched from a start May 27, and he will need to build arm strength before he embarks on a minor-league rehabilitation assignment.

Those factors raise the question as to whether he will return before the All-Star break.

Reliever Carl Edwards Jr. is scheduled to play catch Tuesday for the first time since being placed on the 10-day disabled list May 30 because of right shoulder inflammation.

Iowa-Chicago shuttle: Anthony Bass became the sixth reliever promoted from Triple-A Iowa to join the Cubs with the club needing another fresh arm after Cory Mazzoni threw two innings Sunday and was sent down.

Maddon hasn’t hesitated to use recently called up relievers, and many have succeeded only to return to Iowa because of the need for a fresh arm.

“The pitchers chosen in the offseason to ride that train between here and Triple-A have done very well, and there’s a lot more to choose from than there was last year,” Maddon said.

Dillon Maples could get a promotion in the future. Maples, 26, has struck out 13 while walking none and allowing two hits in his last six innings for Iowa.

Bass, 30, had a 2.28 ERA and three saves in 18 games with Iowa, including a 1.46 ERA in his last 10 games. Bass has pitched in 131 games for the Padres (2011-13), Astros (2014) and Rangers (2015, ’17), as well as the 2016 season with the Hokkaido Nippon Ham-Fighters of Nippon Professional Baseball.

To make room for Bass on the 40-man roster, reliever Eddie Butler (right groin strain) was transferred from the 10-day DL to the 60-day DL.