ARLINGTON -- The Rangers are shutting down pitcher Brandon McCarthy for at least two weeks because of a stress fracture in his right shoulder blade.

The injury could open a way for the Rangers to get Edinson Volquez back in the rotation. John Rheinecker is taking McCarthy's spot against the Kansas City Royals but Volquez could start on Tuesday against the Baltimore Orioles when that spot comes up again.

"He's certainly on our radar," Rangers assistant general manager Thad Levine said. "We're certainly encouraged by the progress he's shown. His performance speaks for itself."

Volquez, who started the season at Class-A Bakersfield, is 5-1 with a 1.89 ERA in six starts at Triple-A Oklahoma. He was the losing pitcher on Tuesday but was still impressive in allowing one run on four hits in seven innings with one walk and 11 strikeouts.

"Of course we want to see Volquez at some point," Rangers manager Ron Washington said. "He's done everything the organization has asked him to do. At some point we have to see what he has to offer up here."

The Rangers expect McCarthy to pitch again this season but it won't be until September. He has been bothered by a shoulder problem since May and it wasn't getting any better, so he underwent an MRI on Monday. That's when the Rangers discovered that he had the stress fracture.

"It wasn't getting any worse but it wasn't getting any better so we decided to check it out," McCarthy said.

A stress fracture normally takes 10 weeks to heal. The Rangers think McCarthy has the worst behind him and shutting him down for two weeks will allow the problem to heal completely.

McCarthy said the problem has affected him more on his off-speed pitches and he hasn't been able to throw the usual bullpen session between starts since the All-Star break. He has a 3.18 ERA in since starts since then even though he hasn't been 100 percent.

He is 5-8 with a 4.79 ERA in 20 games, including 19 starts, and 94 innings on the season.

"I could throw through it and have been [fine] for the most part," McCarthy said. "But I was tired of going out there half-loaded. We'll give it a chance to rest and shoot for three of four starts at the end of the year."

The Rangers see no reason to shut down McCarthy for the rest of the year. Instead, they feel he would benefit from continuing to pitch while building up arm strength and innings.

McCarthy is in his first full year as a Major League starter. He threw 84 2/3 innings -- mainly as a reliever for the White Sox in 2006 -- and the Rangers were hoping to get him up to 140-150 innings this year. That would put him in position to pitch 180-200 innings next year.

The Rangers are still hoping to get him up to 125 innings by the end of the season.

"We won't rush him," Levine said. "We don't feel compelled to pitch him but based on our medical reports, we don't see any reason why he shouldn't pitch."