Pena, out since Aug. 1 with a right plantar fascia sprain, said it felt good to be back with the team, and although he thought he might feel "some discomfort," he said he doesn't expect the foot injury to be a problem going forward.
"I feel good. We're just going to keep progressing, taking care of it, being smart with all the treatment and all the necessary exercises to maintain myself," Pena said. "That's it. I think I should just keep on progressing and shouldn't have any type of difficulty doing that. I don't expect anything to go wrong. On the other hand, I expect everything to go very smoothly.
"I've been really working hard and putting a lot of stress on it over the last week and a half, and it's responded very well. I don't expect it to go backward on me or to get tired or anything like that. I think we've done all that we can."
Pena played a rehab game with high Class A Charlotte on Sunday night, going 2-for-3 with two singles and an RBI as the team's designated hitter -- an encouraging sign for manager Joe Maddon.
"Carlos had a nice day yesterday -- no repercussions, felt really good, hit the ball well," Maddon said. "And they did shift him. We wanted to check on if they did shift him in the Minor Leagues, but Los came through and he's ready to roll."
Maddon added that he would keep an eye on Pena to make sure he feels comfortable on the field, particularly on defense, but he wasn't worried about his ability to run the bases. He noted that he would likely check in with Pena later on in each game to make sure he doesn't need a replacement -- but only if it is absolutely necessary.
"I don't want Carlos off the field if he feels like he can play first base," Maddon said, "So that'll be a discussion on a daily basis with him to find out how Carlos feels."
Pena wasn't as worried about the potential pain, as he was just excited to rejoin the Rays, especially as the team enters the home stretch of what should be a tight pennant race with the Yankees and Red Sox.
"It feels so good, it really does," Pena said. "It feels great to be back. We're in a good position and want to be even better, so we've just got to keep on going."