But Benson is still experiencing some irritation in his right elbow from scar tissue that has grown back in a spot where he had Tommy John elbow reconstruction surgery eight years ago. Benson will have the elbow checked before Sunday to see if he needs the scar tissue removed or if he can continue to pitch through it. He has had two cortisone shots that have not helped.
"I'm not concerned about going to Triple-A and starting," Benson said. "My only concern is I want to make sure I don't go out there and pitch four, five, six innings and feel the irritation like I did [early in the season]."
Benson started the season in the Rangers' rotation and was 1-1 with a 9.00 ERA in two starts before the elbow started bothering him. He was placed on the disabled list April 22 and then was put in the bullpen after he was activated May 6. He has a 7.94 ERA in six relief appearances and was falling into disuse.
The Rangers are hoping he can pitch effectively at Oklahoma City as a starter and be an option in case of injury. The Rangers have concerns about their depth with both McCarthy and Matt Harrison currently on the DL.
"Right now, he'll get an opportunity to be in a rotation," Rangers manager Ron Washington said. "With the way our injuries are going, it's another piece for us, and he's a veteran."
Benson had never been a reliever before this season. Grilli, 32, is a veteran reliever who was 0-1 with a 6.05 ERA in 22 appearances for the Rockies this season, but he has a career ERA of 4.14 in 192 relief appearances over all or part of eight Major League seasons. He was a member of the Tigers' bullpen in 2006, when they went to the World Series, and he was scoreless in five relief appearances in the postseason.
"He throws strikes and keeps the ball on the ground," Washington said. "He's healthy and he pitched well in winning situations in Detroit. We're just looking for him to go out and be Jason Grilli. He doesn't need to try and impress us. He needs to impress himself. If he does that, we'll all be impressed."
Grilli has an above-average fastball and a slider. His biggest concern is control, as he has averaged 4.01 walks per nine innings over his career. The Rangers will use him in middle relief, but he has the ability to pitch multiple innings.
The Rangers acquired him for cash considerations after he was designated for assignment by the Rockies last week.
"I'm pretty excited," Grilli said. "The team is in first place and I'm glad to be here. We were last in our division and now I'm in first. I don't feel like I've done anything to deserve that. I'm not going to make excuses. I'll hold myself accountable. I've got a fresh start and I'm ready for it."
This is Moscoso's second time in the Major Leagues. He was up for a week earlier this month and pitched one scoreless inning on the last homestand against the Athletics before being sent to Oklahoma. He is 4-1 with a 4.10 ERA in 10 games, including eight starts, at Oklahoma City and Double-A Frisco this season.
He could have a short stay, but the Rangers are still undecided if Harrison is ready to come off the disabled list and pitch Thursday against the Blue Jays. He could get another start on a medical-rehabilitation assignment in the Minor Leagues while Derek Holland pitches against the Blue Jays.
If Harrison returns Thursday, Holland would go to the bullpen and Moscoso would most likely go back to the Minors.