SCOTTSDALE, Ariz. -- While D-backs manager Kirk Gibson would like to get Geoff Blum some playing time at third base, he made it clear Tuesday that Ryan Roberts was the starter.

"Ryan Roberts is my third baseman," Gibson said. "Ryno did a great job for us last year and he's going to get the majority of the playing time right now."

Roberts hit his way onto the team last spring and appeared in 143 games hitting .249 with 19 homers and 65 RBIs. Heading into Tuesday's game, Roberts was hitting .205 with three homers.

"It could always be better," Roberts said. "Some days I feel good, some days I feel like I'm searching. I've hit the ball hard, I've hit the ball soft, I've got out. I've gotten base hits doing the wrong thing, I've gotten base hits doing the right thing. I'm not looking too much into it. I'm just trying to get to where I feel comfortable. That's the main thing."

Blum was signed to a two-year deal before the 2011 season but was not a big contributor as he missed 127 games due to injury.

This year, Gibson would like to see Blum get more playing time, but his balky right knee is not at the point where it could sustain an everyday role. Even during the spring, Gibson is taking it slowly with Blum.

"I personally would feel uncomfortable playing him two nine-inning games in a row right now," Gibson said.

Corbin has shot to make Opening Day roster

SCOTTSDALE, Ariz. -- Patrick Corbin was once again impressive Tuesday, so much so that D-backs manager Kirk Gibson did not rule out the possibility of the left-hander beginning the season in the Majors.

Corbin threw five hitless innings against the Rockies at Salt River Fields.

Gibson announced his rotation Monday, so it would appear the only way Corbin would make the team would be as a reliever or if one of the starters gets hurt. It's also possible that the team could deal one of the pitchers expected to make the team, which would open up a spot.

"He's probably not the only one," Gibson said when asked if Corbin had a chance to surprise and make the team. "We mull it over. We've got nine games left so things could happen. There's various things that could happen. He's come out of the bullpen for us, he's started for us and again he's very athletic at what he does."

Regardless of whether he starts the year in big leagues or the Minor Leagues, the fact is that Corbin has made an impression.

"If he should go down there we sure would feel confident bringing him back," Gibson said.

Putting himself on the radar for that was what Corbin set out to do when he reported to Spring Training.

"I've worked hard in the offseason like I do every year," Corbin said. "I just tried to come in here and show them what I can do and I feel like I've done that, come in here, pitched as best I could and just giving it a shot to see what happens this year. I think I've always been pretty confident, but just coming up here and showing you can throw against these guys helps a lot."

There's no doubt he's done that as his five scoreless innings lowered his spring ERA to 0.57.

Worth noting

•  RHP Daniel Hudson pitched in a Triple-A intrasquad game Tuesday so as not to give the division-rival Rockies another look at him before the regular season. Hudson allowed one run on four hits over six innings. He threw 84 pitches, 61 strikes and walked one while fanning eight. Hudson will make one more spring start before throwing the season's second game April 7 against the Giants. "I feel pretty close," he said. "My pitch count is up there high enough to go for Opening Day. My arm feels great, the ball feels real good coming out of my hand so the season can't come soon enough."

•  First baseman Lyle Overbay was 2-for-3 on Tuesday to raise his spring average to .256. D-backs manager Kirk Gibson said hitting coach Don Baylor asked Overbay to make some changes at the plate around a week ago. "He's been working on it every day," Gibson said. "Maybe the results aren't what you might think is good, but we're seeing what we're trying to work on -- his posture at the plate, the way he approaches the ball, his swing path. It takes time. It really takes time just to break some bad habits."