TUCSON, Ariz. -- One of Tony Pena's problems last year was consistency.
He had the same trouble in his spring training debut on Saturday.
"It's crazy," Pena said. "I've never seen that before."
The inning was reminiscent of last season, when Pena was either very good or very bad.
Pena opened the season with five consecutive scoreless outings, then gave up six earned runs in his next three games.
He allowed one earned run from May 16 to June 13, then yielded 12 earned runs between July 10 and Aug. 9.
"It's just going be staying out of those stretches, whether it's a couple weeks or three, four outings," manager Bob Melvin said. "Sometimes it's more mental than anything else, but he's a very talented guy. Once he puts together a full season where he's pretty consistent, he'll be off to the races."
Chad Qualls is Arizona's closer, but the other bullpen roles are up for grabs. Pena is likely to be Melvin's main setup man, but Melvin won't hesitate to bring him in earlier if needed.
"Tony is a versatile guy," Melvin said. "He can close, he can set up. He can strike you out, he can get a groundball."
Asked if sees Pena as a future closer, Melvin said, "I do. But you have to earn it. He knows that."
Pena said he doesn't have a favorite role.
"Whatever 'Bo Mel' needs -- eighth, seventh, sixth (innings)," said Pena, who leaves Sunday to join the Dominican Republic as it prepares for the World Baseball Classic.
Brandon McCarthy also had an up-and-down outing in his first start for the Rangers, giving up two runs and two hits in two innings. He walked one and struck out one.
McCarthy, a candidate for the fifth spot in the Texas rotation, is trying to develop a slider this spring. He said he threw six or seven sliders; Mark Reynolds hit one for an RBI double and Josh Whitesell hit another for a run-scoring single.
"It's got to become a consistent pitch where, one, I can find the release point with it every time and, two, do the things I want to do with it," McCarthy said.
If McCarthy can command his slider, he won't have to rely as much on his curveball, which is hard on his arm.
"That curveball, I really torque and try and throw as hard as I can," McCarthy said. "It's something where my arm just kept breaking down with it, so it's giving the slider a shot right now. It's a little more natural. I throw it more like a fastball, so hopefully that lessens the stress on my arm."
McCarthy's first two years with the Rangers have been marked by four trips to the disabled list. Right shoulder inflammation and finger injuries limited McCarthy to five games last year, when he went 1-1 with a 4.09 ERA.
Arizona ace Brandon Webb, scratched from his first spring start with a sore right forearm, is scheduled to throw a bullpen session on Sunday. If all goes well, he'll start on Wednesday against Mexico in Tucson. ... Jones struck out twice, leaving him 1-for-9 with eight strikeouts this spring. ... Texas SS Omar Vizquel was scheduled to make the trip but stayed home with tightness in his right side. ... Arizona OF Chris Roberson hit a solo homer. ... The Rangers and Diamondbacks will play an interleague series in Phoenix from June 23-25.