Butcher working with Escobar on arm angle

Peralta set to begin rehab assignment Saturday

Butcher working with Escobar on arm angle

CHICAGO -- D-backs pitching coach Mike Butcher has worked on left-hander Edwin Escobar's mechanics since he struggled Monday in his start against the Astros.

Escobar is scheduled to pitch Saturday against Jason Hammel.

The start vs. Houston was Escobar's first in the big leagues and just his third overall appearance. He struggled to throw his breaking ball for a strike, and what concerned the D-backs was the fact that he used multiple arm angles when throwing it.

"We're trying to kind of limit that, find one that works best for his breaking ball," D-backs manager Chip Hale said. "I think it's just limiting some of the things he does. The arm is incredible -- up to 95, 96 mph. If we can harness it, we might have something special."

Worth noting

• Outfielder David Peralta (right wrist injury) was 2-for-6 Thursday in extended spring camp. He will head to Triple-A Reno for rehab games Saturday and Sunday, and the club hopes to activate him Monday.

• The D-backs took batting practice on the field at Wrigley on Friday. It will be the only on-field mandatory session of the series. Saturday and Sunday, there will be optional batting practice on the field, with hitters having the option of taking their swings in the indoor batting cage instead.

Steve Gilbert has covered the D-backs for MLB.com since 2001. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.