CHICAGO -- Cubs first baseman Carlos Pena may want to come back as soon as he can. Tyler Colvin looked pretty good at first on Tuesday, his first start there in the big leagues.

Pena did not play Tuesday in the Cubs' 6-5 win over the Diamondbacks because of a mild sprain of his right thumb, suffered in Monday's game.

"He's day to day," Cubs manager Mike Quade said of Pena. "We could probably use him if I needed to late. We'll be careful. We get a chance to watch Mr. [Tyler] Colvin at first base."

Colvin did just fine, including scooping up shortstop Starlin Castro's throw on pinch-hitter Xavier Nady's hard-hit ball for the second out of the ninth.

"I guess he was ready," Quade said of Colvin.

"I'm ready for wherever [Quade] wants to put me," Colvin said.

Pena injured his thumb in the D-Backs' seventh Monday, when he fielded Gerardo Parra's grounder.

"I made a play, it was a ball in the hole, I think it was in the seventh when [Sean Marshall] came in to pitch," Pena said. "As I threw the ball, I fell to the side and put my glove hand down and I think I jammed it into the ground.

"I told [Quade], 'Do you need me? I'm ready to go,'" Pena said. "We're trying to be cautious. If he needs me to pinch hit or anything, I'm out here working to keep it nice and loose."

Pena said his thumb was more uncomfortable than painful.

"I've been in worse pain before," he said. "I'm available. That was my message to 'Q.'"

Pena said it was a freak injury, and the first time he's jammed the thumb on his glove hand. He knows the athletic trainers will be cautious.

"I always try to push myself too much at times, so maybe it was not rational for me to think I was going to start today," he said. "I feel like tomorrow there's a pretty good chance."

Pena tutored Colvin this spring at first base. Colvin got the start Tuesday, his first in the big leagues there. Before the game, Pena was asked on the possibility of Colvin going 4-for-4?

"I hope he does -- not Wally Pipp me, but I hope he hits four home runs," Pena said.

Colvin delivered one, a two-run blast in the third, and also drew a walk with the bases loaded against lefty Joe Paterson in the seventh, which gave the Cubs a 6-4 lead.

"Off the starter [Barry Enright], I saw how he pitched me the first at-bat, and I tried to go off that and get better timing," Colvin said of the home run at-bat. "A tough lefty coming against me, he's trying to throw strikes. I wanted to see one and he didn't give me one, and I got the walk."

Colvin had only played in the outfield in the big leagues.

"The first time I saw him there, I was like 'No,' but it was my perception, not that he wasn't doing a good job," Quade said. "The more I saw him, the better I felt. Again, lack of experience will make it a heck of a challenge for him. He's willing and has decent hands. It didn't take a second to think about it when Carlos couldn't go."

The extra time will also benefit Pena, who fouled a ball off his right foot on Monday.

"If he walks in here [Wednesday] and says, 'I'm 100 percent,' he plays," Quade said. "I want that to be the case, and I don't want him to come back and have something that's going to linger for weeks or more. We'll take a look at that."

Don't expect Pena to be wearing a guard despite fouling a pitch off his foot. That happened in the sixth on Monday; he hurt his thumb in the seventh.

"[My foot] hurt," Pena said. "After I hurt my thumb, I forgot about [my foot]."

Hard-working Marmol, Wood earn day off

CHICAGO -- And on the fourth day, Carlos Marmol and Kerry Wood rested.

Marmol and Wood, who have appeared in three straight games for the Cubs, were told they had Tuesday off by manager Mike Quade. He's got plenty of other options to back up starter Andrew Cashner, such as Jeff Samardzija, James Russell and Marcos Mateo.

"My bullpen is in great shape," Quade said. "I've got five guys ready to help us finish a game. When you take a shot at using two guys like I did three days in a row this early, that's that.

"You've got a better chance seeing me pitch today than you do Woody or Marmol. They did a great job. They said they felt good, so we took a shot. I'd prefer not to do that."

Quade had asked both Marmol and Wood if they were available Monday, and both said yes. However, the manager does reserve the right to overrule them.

"I told them, 'I need to trust you guys, and it doesn't mean I'm always going to trust you,'" he said.

Extra Bases

CHICAGO -- Starlin Castro continues to dazzle both the Cubs and opponents with his defense. Said Arizona manager Kirk Gibson: "The shortstop made three exceptional plays. He was the player of the game for them as far as I'm concerned." One of the plays came in the ninth when Castro recovered pinch-hitter Xavier Nady's hard-hit ball and threw him out. ... James Russell pitched 1 2/3 scoreless innings in relief, and also got an at-bat in the eighth. It was his fifth career at-bat, and he struck out. "It would've been great to get a base hit," Russell said. ... Jeff Samardzija walked two and both scored in his one inning of relief work Tuesday. After the game, he was throwing against the wall in left field by himself. ... When Bobby Dernier played for the Cubs in 1984, he doesn't remember ever having to deal with seagulls in the outfield. Lately, the birds have been flocking to Wrigley Field, and on Monday it was tough for center fielder Marlon Byrd to catch Justin Upton's ball for the final out. It's hard to see a white ball amid all the white seagulls. The birds are scavengers looking for leftover hot dog buns, peanuts and sunflower seeds. ... The Cubs' Class A Peoria Chiefs will face the Timber Rattlers at Miller Park on June 29 in a Midwest League game. The Chiefs have played in a Major League Baseball stadium in each of the last three seasons, including two games at Wrigley Field in 2008 and '10. "It's a great opportunity for these guys to play in a venue that they are all striving to get to," Chiefs manager Casey Kopitzke said.