Pena (calf) will begin a rehab assignment with Triple-A Sugar Land on Tuesday, Brian McTaggart of MLB.com reports.
Pena is less than a week removed from landing on the 10-day injured list with a left calf strain, but he's ready to test things out in a game setting. The expectation is that Pena will play a couple rehab contests before being activated from the IL on Friday when he's first eligible.