WASHINGTON -- Cubs pitcher Ryan Dempster threw what he called an "epic" side session on Thursday and said he expected to start the second game of a three-game series against the Pirates on Saturday.

Dempster missed his Monday start because of back soreness and stomach problems. He was hospitalized overnight for observation on Saturday. But on Thursday at Nationals Park, he was able to do a normal side session in the bullpen and then went for a run with pitcher Chris Carpenter.

"As long as I feel good [Friday], I don't see any reason why I can't pitch on Saturday," Dempster said.

Cubs manager Mike Quade didn't want to commit to Dempster until he sees how the right-hander feels on Friday.

"He hasn't exerted himself like that with a side since all this went down and since his last start," Quade said.

Dempster joked that his side session was "epic," and possibly the best he's thrown all year. But he was a little nervous when he was in the hospital.

"When you're laying there in a hospital room and don't have the answers, you wonder," Dempster said. "They took good care of me and hopefully everything is all right."

The Cubs, who have put 13 players on the disabled list in the first half and used 10 starting pitchers, can use some good news, and having Dempster return would qualify.

"If you sit there and sulk, nobody on the other side of the field feels sorry for you," Dempster said. "Why feel sorry for yourself? We've lost before, whether it's as individuals or as a team. We've lost games whether it's here or somewhere else. The easiest way to get through that is to stay upbeat and focus on today's game.

"We can file all the appeals we want to the league, but we can't get those games back. The easiest way is to focus on winning today's game and not where we'll be at the All-Star break, just today."

Big Z to make rehab start Friday

WASHINGTON -- Cubs pitcher Carlos Zambrano, on the disabled list with lower back soreness, will make a rehab start on Friday for Class A Peoria.

If all goes well, Zambrano could be back in the Cubs' rotation for a July 16 start against the Marlins at home.

Cubs manager Mike Quade's brother Scott caught Zambrano in a side session on Wednesday at Wrigley Field.

"If you've caught him before, then you know what a Zambrano side is like," Quade said. "[My brother] told me, 'He's the same as the guy I caught last year' and thought he threw fine. It was a productive day for [Zambrano]."

Zambrano is headed to Guatemala on Sunday to finalize paperwork to adopt a 2-year-old boy, whom the pitcher met when he was 5 months old. Zambrano's Big Z Foundation is taking 100 pairs of shoes to donate to the orphanage where the boy currently lives.

Ex-Buc Grabow happy for Pirates' success

WASHINGTON -- The last time the Cubs played the Pirates on May 29, Pittsburgh was 24-27 and 6 1/2 games back, while Chicago was 23-28 and 7 1/2 games back. Now, the Pirates are above .500 and within 1 1/2 games of first in the National League Central.

"It's cool that they're playing well," former Pirates pitcher and current Cubs pitcher John Grabow said. "The city deserves that. It's a big sports city. The fans have been waiting for a while for a winning team. We're going to go in there and try to spoil some stuff."

When Grabow played in Pittsburgh from 2003-09, times were tough.

"The Steelers, the Penguins, even college basketball is huge there," he said. "When I was there, we were last in line. It was frustrating, because you go to a Steelers game and it's crazy, you go to a Penguins game and it's fun. We'd go through little stretches where we played well and then we didn't play well.

"It seemed like the only time we sold out was when there were fireworks or a giveaway. The fans supported the team, but they weren't selling out. It's a shame, because it's such a beautiful stadium and fun to play at. It'll be fun to go there and see how many fans they get."

Pena thoroughly impressed by Castro

WASHINGTON -- Carlos Pena has played with a number of shortstops over the years, but none as young or as talented as the Cubs' Starlin Castro.

"To see him come in and do so well and hold his own is very impressive," the first baseman said Thursday of the Cubs' All-Star representative. "It just shows you how talented he is. At this moment, the talent carries him. He doesn't have enough time in the league to use experience as an asset. Having said that, it's very exciting, because as he acquires more knowledge, you wonder how much better he can be."

Pena was named to the 2008 All-Star Game and was one of the first to congratulate Castro on being selected to the National League team for Tuesday's game at Chase Field in Phoenix.

"He's humble, respectful of the game and up to this point -- even though he's had incredible success and has confidence -- he has the attitude that 'I don't know it all' and that's the perfect combination," Pena said of the 21-year-old shortstop. "It's almost like he has all the tools necessary to be an impact player for many years to come."

What Pena likes is that Castro keeps working in the batting cage and on the field to get better.

"It's one thing to be confident, which he is, but to stay that humble, which he has been, I can see success coming his way," Pena said.

Extra bases

• The Cubs expect to get results on Friday from the MRI on pitcher Marcos Mateo's right elbow. Mateo was placed on the disabled list Tuesday because of soreness in his right elbow. He had returned to Chicago for the test.

• Infielder Jeff Baker remained day to day after coming out of Tuesday's game with back spasms. Baker was able to take batting practice on Thursday.

• The Office of the Commissioner of Baseball announced Cubs Minor League pitcher Enyelberth Pena received a 50-game suspension after testing positive for metabolites of Nandrolone. That's in violation of the Minor League Drug Prevention and Treatment Program. The suspension of Pena, who was currently on the roster of the club's Dominican Summer League affiliate, was effective immediately.