SCOTTSDALE, Ariz. -- Jason Frasor is on the same program as Rangers closer Joe Nathan. Because Spring Training is long this year, the Rangers are holding back their two veteran relievers and have not let them throw in a game yet.

Instead they are doing their throwing in the bullpen and in live batting-practice sessions. Nathan threw 10 minutes of live batting practice on Monday, and Frasor is expected to throw on Wednesday. The two have a combined 1,143 appearances in the Major Leagues, and the Rangers are going to bring them along slowly.

"They have been around awhile," manager Ron Washington said. "They don't need to go out there for 12-13 innings, so we're slow-pacing them."

Nathan has 618 big league relief appearances and Frasor has 525. Joakim Soria is third on the Rangers with 298 appearances. Soria, who had Tommy John surgery on April 3, threw 35 pitches in a bullpen session on Monday. He is expected back in May.

Rangers optimistic Lewis could return in May

SCOTTSDALE, Ariz. -- Colby Lewis threw off a "half mound" on Monday morning. He didn't think it was a big deal, but the Rangers did.

"I'm moving up six inches maybe," Lewis said. "I'm going throw it a little bit and see how it feels tomorrow. It's not like I'm going to get up on the mound and rev it up."

Instead he threw 20 pitches off the lower slope of a regular mound without a problem, and it's another step in the process. Lewis, who was the Rangers' Opening Day starter in 2012, had surgery to repair a torn flexor tendon in his right arm on July 27, and the target date for his return is June 1.

But Lewis continues to make significant progress and Texas is growing optimistic he could return sometime in May. The Rangers are hoping that Lewis can start throwing off a full mound by this weekend.

Lewis is the X-factor in the Rangers' deliberations regarding their fifth starter. If it appears that he will indeed be back in May, it could influence the club's decision.

The Rangers have seven candidates for the fifth spot, including four rookies -- Martin Perez, Justin Grimm, Nick Tepesch and Cody Buckel -- who could need more time in the Minor Leagues. They have veterans Randy Wells and Kyle McClellan. Wells has impressed early in camp, while McClellan is sidelined with soreness in the back of the right shoulder.

Then there is Robbie Ross, who was Texas' best setup reliever last season and is being given a real shot to make the rotation. But if Lewis looks like he'll be back in May, the Rangers may decide to leave him in the bullpen.

Instead the Rangers might decide to go with Wells until Lewis is ready to return within the first two months of the season.

McClellan, who had shoulder surgery in July, was throwing the ball well early in camp, but came down with muscle soreness behind the shoulder last week. He tried to throw on Sunday, but had to be shut down because of the soreness. He may try again Wednesday, and there is still time for him to get back in the competition.

Berkman could be game-ready by this weekend

SURPRISE, Ariz. -- Rangers designated hitter Lance Berkman could be ready to play in a game by the end of the week. Wednesday is a possibility, but Thursday or Friday is more realistic.

Berkman has not played in a game because of a strained right calf muscle, but he has been able to run the bases and take ground balls without any issues lately. The Rangers have been cautious with both Berkman and Adrian Beltre because of the cold weather. The veterans had no trouble running the bases on Monday.

"This is not a big deal at all," Berkman said.

Outfielder Engel Beltre may have the more significant injury. He has some soreness in the back of his left shoulder, and it could keep him from playing for Spain in the World Baseball Classic. The Rangers do not believe the injury is serious, but it's still something they are watching. Beltre is supposed to join Spain this weekend.

"We feel and Spain feels he would have to get back to game speed," Rangers assistant general manager Thad Levine said. "There would be some reluctance to put him in a game for nine innings if he's not ready."

Worth noting

• The Rangers, after a 9-1 loss to the Rockies on Monday, have four hits in their last 32 at-bats with runners in scoring position, and manager Ron Washington said, "We're aware of it. Once again, it's Spring Training. We're behind offensively, but we'll catch up and start executing."

• Texas' best hitter so far has been Leonys Martin. He didn't play Monday, but is 3-for-6 so far in the Cactus League, and Washington said, "He knows he has a chance to make the team and came ready to play."

• The Rangers were able to use the designated hitter on Monday despite the game being played at the Rockies' complex that they share with the D-backs. Said Washington, "Colorado is pretty good at letting us use it, but Arizona usually doesn't let us use it."

• Reliever Tanner Scheppers remains sidelined with a strained left hamstring.

• Wilmer Font (shoulder inflammation) threw 75 feet without any pain on Monday.