ST. LOUIS -- Cardinals shortstop Jhonny Peralta will take the next step in rehabbing his left thumb on Friday when he starts a rehab assignment with the Class A Peoria Chiefs.

Peralta is over two months into his recovery after injuring the thumb in Spring Training when he fielded a ground ball on March 5. He underwent surgery on March 10 and began defensive drills and fielding work in early May.

"It's a little different than your typical rehab stint in that you have to figure out how to get yourself in playing situations and play in shape, which he hasn't been in," manager Mike Matheny said. "We've got something mapped out. It's always subject to change, but he'll be getting shorter starts in the beginning and days off scheduled in there and stretch him out as we go."

General manager John Mozeliak noted earlier this week that the Cardinals will "not rush" Peralta back to the big leagues. His rehab assignment can last a maximum of 20 days.

Matheny expects Peralta to play at shortstop and third base during the rehab stint in part to try and find a way to keep Aledmys Diaz in the Cardinals' lineup. The rookie entered Thursday hitting .376 and slugging .648, both second-best in the National League. Peralta's presence in the field has been missed, as Diaz has committed a Major League-high 10 errors this season.

Peralta took batting practice with the team on Wednesday, and Matheny was pleased with the results.

"He's been a great patient from what I hear," Matheny said. "Kind of staying on course with what everybody is asking him to do, and he's reaping the benefits of that."

Nick Krueger is a reporter for MLB.com based in St. Louis.