CINCINNATI -- Rookie Esmailin Caridad could join the Cubs as soon as Sunday.

The right-hander threw two innings on Thursday in his second rehab outing for Triple-A Iowa and gave up one run on one hit, a home run, while striking out one. He did not walk a batter.

Caridad has been sidelined since April 12 because of a strained right forearm and could rejoin the team in Cincinnati.

The team will need to make a roster move and would most likely send one of the other right-handers -- either Jeff Gray or Justin Berg -- to Iowa.

Theriot handles position switch with grace

CINCINNATI -- In February, almost from the first day Ryan Theriot showed up in Mesa, Ariz., he was asked about Starlin Castro. Theriot knew that at some point the young shortstop was going to take over on the big league team.

But Theriot didn't find out it would be Friday until sometime the day before.

"You just prepare yourself for it," Theriot said on Friday. "He was playing great. From a team standpoint, any little spark is welcome right now. When your first thought is not yourself but the team and you want to win ballgames, that's accepted, and you hope it works out."

General manager Jim Hendry has talked to Theriot to prep him for Castro's arrival.

"In Spring Training, it was pretty evident," Theriot said. "Everybody knew it was coming. It's going to make our team better. Hopefully, it'll kick-start things. We'll see."

Hendry praised Theriot for what he's done for the Cubs at shortstop and how he accepted the switch. He has been the regular since 2007, and the Cubs have won two National League Central titles with him in the lineup. On Friday, Theriot was starting at second base, his new spot.

"I took some ground balls today to get used to being on the opposite side of the diamond," he said. "It should be an easy transition."

However, moving Theriot to second means that Mike Fontenot and Jeff Baker will have limited playing time. The two were sharing second base already.

"They become utility players," manager Lou Piniella said of Fontenot and Baker. "I like both of them. They're both good players. Right now we're going to go with the young kid at short and Ryan at second, and hopefully, it gets us better."

Fontenot came through on Friday, delivering a pinch-hit grand slam in the eighth inning of the Cubs' 14-7 win over the Reds. It was the first slam by a Cubs player off the bench since Derrek Lee did so on May 19, 2007, against the White Sox.

The Cubs are happy to have not only Castro's bat in the lineup but his glove.

"[Castro and Theriot] have a wonderful chance of being a good double-play combination for a long time," Piniella said.

"I'll do everything I can in my power to make sure he's comfortable and make sure the transition is a smooth and easy one for him," Theriot said of the 20-year-old Castro, "the same way [Mark] DeRosa and [Derrek Lee] did for me when I was breaking in."

Piniella wants Wells to put outing behind him

CINCINNATI -- Randy Wells was upset after his outing on Thursday, in which he lasted just two innings against the Pirates.

Manager Lou Piniella talked to the right-hander on Friday.

"I told him, 'You're too hard on yourself,' " Piniella said. "Everybody's entitled to a bad game. Cy Young lost a few games.

"[Pitching coach] Larry [Rothschild] told me he threw the ball better than he had at any time this year," Piniella said. "He probably got a little full of himself and lost a little bit of concentration on the mound, and that's what happens. You take that as a learning experience. Don't beat yourself up."

Wells offered a 75-second explanation for his outing without needing a question to get started, saying his outing was "terrible" and "unacceptable."

On Friday he was running up and down the steps at Great American Ball Park, doing his cardio work. He'll get his next chance on the mound on Tuesday against the Marlins.