TORONTO -- Outfielder Frank Catalanotto could be headed to the disabled list with a right shoulder injury, pending the results of an MRI examination on Tuesday.

A final decision has not been made. Catalanotto wasn't in the Rangers' lineup on Monday and manager Ron Washington doesn't want to wait too long for him to be available. Victor Diaz, who is hitting .356 with three home runs and 28 RBIs at Triple-A Oklahoma, would likely be brought up. He was not in the lineup for the Redhawks on Monday.

"We can cover ourselves tonight, but I don't want to have to cover myself every night," Washington said. "If it doesn't get any better, we may have to do something."

Catalanotto injured his shoulder making a throw in Sunday's game against the Blue Jays, and is concerned he might have torn something. Catalanotto had surgery on the shoulder 10 years ago and it may be just scar tissue. The Rangers are waiting to see what the MRI shows.

Catalanotto said the shoulder was better on Monday, but still aching.

"It's like a full aching feeling from the shoulder to the bicep," Catalanotto said. "It felt like it was tearing. I don't know if it was scar tissue or I tore something. When it happened, I was scared I did something terrible to it. In talking to Eric Gagne and the trainers, they think it may be nothing more than scar tissue and it could be better in 24 or 48 hours."

If Catalanotto is going to be out longer than that, he'll likely go on the disabled list.

"Even if it's not serious, we'll have to gauge how long he's going to be down," general manager Jon Daniels said.

Gagne likely to rehab: Gagne isn't done pitching in the Minor Leagues. The Rangers are planning to send him out on a medical rehabilitation assignment before they activate him off the disabled list.

"I wouldn't put him right back out there," Daniels said.

On Monday, Gagne threw for the first time since going on the disabled list last week with a strained right hip. Gagne said everything went fine and the Rangers are hoping he can be ready to throw off a mound by Friday. The next step will be a rehab stint.

"I'd like to get him two or three outings," Daniels said. "The first step will be to get a good bullpen session off the mound."

Littleton flies in: The Rangers sent for Triple-A Oklahoma pitcher Wes Littleton on Monday, but decided against activating him.

Littleton, flying in from New Orleans, might have been added to the roster, but his plane was late getting to Toronto because of mechanical problems. The Rangers are taking him with them back to Arlington and may add him on Tuesday if there is a need in the bullpen.

The Rangers were concerned about being short on pitchers after Brandon McCarthy pitched just three innings on Sunday against the Toronto Blue Jays. But they were hoping Vicente Padilla could get them through Monday without wearing down the bullpen.

"Our starters need to get us deeper in the game," Daniels said. "The bullpen has done a great job, but we don't want to overuse them in the first month."

Daniels on McCarthy: McCarthy has allowed 17 runs over just six innings in his last three starts, but is still scheduled to pitch on Friday against the Blue Jays. Daniels didn't want to get into how long the Rangers would stay with McCarthy if he continues to struggle.

"I'm not about to do that with any player," Daniels said. "It's not fair. He just needs to relax more in game situations. I expected him to be better in the second half than the first half as you would with any young player. He's certainly capable of pitching better and I think he'll make some improvements."

McCarthy walked four and hit a batter on Sunday and Daniels said, "Brandon has always gone out there with tremendous command. I always took it as a given that he would throw strikes, but he struggled with that yesterday."

Wright to start throwing: Jamey Wright, who is on the disabled list with shoulder inflammation, is expected to resume throwing on Tuesday when the Rangers return to Arlington.

"He feels really good about all the exercises he has been doing," pitching coach Mark Connor said. "We'll see how he is when he cocks his arm and throws the baseball."

He said it: "I think I'll call Chipper Jones and congratulate him on making baseball history." -- Rangers shortstop Michael Young, on the unassisted triple play turned by Rockies shortstop Troy Tulowitzki on Jones' line drive

Sunday's Minor Stars: The top performances from Sunday's Minor League games:

Gold: Clinton pitcher Michael Ballard allowed two runs on six hits in six innings in Clinton's 5-3 victory over Great Lakes. He struck out two and did not walk a batter.

Silver: Third baseman Chris Davis was 3-for-4 with a double and an RBI and outfielder Terry Blunt went 3-for-4 with two runs scored in Bakersfield's 7-5 victory over Lancaster.

Bronze: Infielder Adam Fox went 3-for-4 with a double, a walk and two runs scored in Frisco's 5-4 loss to Corpus Christi.

Briefly: Second baseman Ian Kinsler went into Monday's game with nine home runs, tied for the most in the month of April in club history. Kinsler and Sammy Sosa (7) have combined for 16, and that's one short of the record by two Rangers combined in the month of April. ... Washington on the month of April: "A lot of good things happened and some bad things happened. The bad thing was we had no luck. You need luck in baseball and we had none. Those 10 wins, we earned every one of them."

Up next: The Rangers return home and open a three-game series with the New York Yankees at Rangers Ballpark in Arlington, beginning at 7:05 p.m. CT on Tuesday. Right-hander Kameron Loe pitches for the Rangers against right-hander Philip Hughes for the Yankees.