SCOTTSDALE, Ariz. -- Jeff Samardzija was roughed up for more runs in one inning than he'd given up in three previous outings, but the Cubs right-hander blamed mental mistakes and said he'll learn from it.

Samardzija had given up three runs on six hits over 10 innings in his three previous Cactus League outings, but the Rockies topped that in the second inning on Friday.

Chris Nelson led off with a home run and the Rockies loaded the bases on three singles, two of them infield hits. Carlos Gonzalez then cleared the bases with a double to take a 5-3 lead.

"The ball was up all day," Samardzija said. "Against this team, they're pretty free swinging and I'm a power pitcher. If I'm down in the zone, it turns into quick outs. If not, you see a cutter there, it gets fisted out, it gets over second base, things like that. Those balls are down, they're ground balls and you're moving on. I need to make a quicker adjustment. It's just a couple pitches here or there to improve on."

Samardzija, a strong candidate for one of the vacancies in the Cubs' rotation, settled down in the third and retired the side in order.

"It felt great to do that and apply what I needed to do, come out and pound the zone with my fastball and be aggressive," he said.

Samardzija did help himself in the fourth, hitting a tie-breaking RBI single. Geovany Soto belted a pair of two-run homers and added an RBI single for the Cubs.

"That's the other frustrating part is when your offense gives you six, seven runs and you can't capitalize on that as a pitcher, that's not good," Samardzija said.

Cubs manager Dale Sveum named Ryan Dempster the Opening Day starter on Friday. Matt Garza and Paul Maholm also have secured spots in the rotation. What does Samardzija have to do?

"All I have to do is keep pitching," Samardzija said. "I'm very happy with how things are going and how I'm pitching and I'm just going to keep throwing and they'll make the decision when they make the decision."

Randy Wells, Rodrigo Lopez and Chris Volstad are also battling for those spots.

"You need to keep showing them that you're out there improving and getting ready for the season," Samardzija said.

That's something Dempster will probably be reminding Samardzija of. The veteran took Samardzija under his wing this offseason and the two trained together in Arizona, beginning in November.

"If [Dempster] had a day like this, he'd go out and get his work in and take positives from it and take the negatives and learn from it," Samardzija said. "That's what I'm going to do. I'm really not worried about it. It's the way it went. I'm more upset with not making the adjustments I needed to make at certain times."

Sveum has made it known how much he likes what Samardzija has done this spring -- and what he could do in the rotation.

"You never doubt the importance of a 6-foot-6, 230-pound horse on the mound," Sveum said. "Every organization thrives for either developing or somehow acquiring somebody like that."

Bullpen decisions may wait until roster deadline

SCOTTSDALE, Ariz. -- Who makes the Cubs bullpen may not be known until the last days of camp.

Cubs manager Dale Sveum said Friday he'd like to have the final 25-man roster set before the team leaves for Chicago in one week, but admitted that may not be possible.

Carlos Marmol and Kerry Wood are set and the rest are to be determined. One player who has stood out is Rafael Dolis, who has struck out three over six innings, giving up two hits and walking one.

"Dolis has a power arm, throws strikes, has an impressive sink," Sveum said. "He's had a heck of a spring. It'd be tough not to say he's going to be possibly one of the guys. He's got too good stuff and has done too well this spring."

The Cubs need to find another set-up pitcher because they know Wood isn't as durable as in the past. Dolis may be that guy.

"The only thing is can they handle that [job] when they have a lead," Sveum said. "The only way you get experience is doing it and finding out. His stuff is electric stuff. There's no hitter who likes facing that kind of stuff. We'll just have to wait and see what role it is."

One of the pitchers currently a candidate for the rotation, such as Rodrigo Lopez, could go into the bullpen as a long man.

"The resiliency of those guys is very important," Sveum said.

Extra bases

SCOTTSDALE, Ariz. -- Ian Stewart's last homer in the big leagues was Aug. 23, 2010, so it's understandable that he was pumped after connecting on Thursday against the Rangers. Sveum said the Cubs are counting on the corner players -- Stewart and Bryan LaHair -- to provide power.

"He's put some good swings on the bat all Spring Training and hasn't had any poor at-bats," Cubs manager Dale Sveum said Friday. "It's huge to get that monkey off his back, even though it was Spring Training. He hasn't hit a home run in a Major League game for quite a while. I think that was a big relief for him."

• Ryan Dempster, named the Opening Day starter on Friday, will make his next spring appearance on Sunday in a Minor League game at Fitch Park. Rodrigo Lopez will get the start against the Indians in Goodyear, Ariz. On Monday, the Cubs have their last split-squad games of spring, and Paul Maholm will face the Padres in Mesa, Ariz., while Jay Jackson starts against the Diamondbacks in Scottsdale, Ariz.

• The Cubs did not provide an update on Marcos Mateo, who had to leave Thursday's game with arm discomfort.

"It didn't seem to be all that promising yesterday," Sveum said Friday.

While at Triple-A Iowa, Mateo was placed on the disabled list last July 5 with right-elbow soreness and missed the remainder of the season.