Castro missed 31 games because of swelling and excess fluid in his surgically repaired right knee.
"I'm excited to get back," said Castro, who hit .301 with two homers and 12 RBIs in 83 at-bats before going on the DL. "I felt really comfortable and just relaxed at the plate, and hopefully I can keep that up here and kind of pick up where I left off before [going on] the DL and even during my rehab assignment."
Castro combined to hit .556 with three doubles, a home run and two RBIs in seven rehab games between Double-A Corpus Christi and Triple-A Oklahoma City. More important, he caught back-to-back nine-inning games on Friday and Saturday.
"The ultimate goal was to get to where I was comfortable catching back-to-back nine and being able to do it comfortably," he said. "It felt good, and it went as planned and as hoped, so I'm excited to be back."
Manager Brad Mills plans to alternate between Castro and Chris Snyder every other day for the next week.
"We hope that's enough so when we do need to play [Castro] back to back, he's played enough and built up to that," Mills said.