MINNEAPOLIS -- Michael Kirkman, who is establishing himself as a key member of the Rangers' bullpen down the stretch, has been named the Pacific Coast League's Pitcher of the Year.

Kirkman, before being called up to the Rangers on Aug. 20, was 13-3 with a 3.09 ERA in 22 starts and two relief appearances at Triple-A Oklahoma City. In 131 innings, he allowed 115 hits and 68 walks while striking out 130. Even though he has been gone for two weeks, Kirkman's 3.09 ERA is still the third best in the PCL and he is tied for the second in wins and strikeouts.

The Rangers have been using Kirkman out of the bullpen, but manager Ron Washington said he still has a future as a starter.

"We like his stuff," Washington said. "He has an explosive fastball and a very good breaking ball in and out of the zone. It also looks like he has some mound presence and has become a guy who consistently pounds the strike zone."

Kirkman, 23, was a fifth-round pick in the 2005 First-Year Player Draft out of Lake City (Fla.) High School who has pitched eight scoreless innings since joining the Rangers, allowing six hits and two walks while striking out eight.

Hamilton returns, but lower back stiffens up

MINNEAPOLIS -- Josh Hamilton continues to feel significant improvement in his aching right knee and was back at designated hitter on Friday.

Hamilton went 2-for-4 in a 4-3 loss to the Twins, but he had to leave the game in the eighth inning with stiffness in his lower back after a single to right. Hamilton said a joint in his lower back locked up on him.

"I never felt it until I came out of the box," Hamilton said. "I got to first and felt they better get somebody in there to run."

Hamilton said they were able to get the joint loose after he came out of the game. He said he expected to be able to play the outfield on Saturday. He has had this problem before but always on the right side. This was on his left side.

"I don't see it being a problem," Hamilton said. "I'll be good to go."

Hamilton was at designated hitter on Friday because manager Ron Washington wanted to get Vladimir Guerrero a night off. Coupled with the off-day on Thursday, that would give him two straight days off.

"I had already talked to Guerrero about this day off in Kansas City," Washington said.

Hamilton has been bothered by the knee on and off all season. He has had two cortisone shots earlier this year and had a lubricant injection on Monday in Kansas City. He said he is noticing a difference since then.

"I feel a lot better," Hamilton said. "I don't feel it aching like it was. That was the worst part. It felt like a toothache in my leg."

Hamilton was the Rangers' DH on Monday and Tuesday and was given the day off on Wednesday. He is still leading the Majors with a .362 batting average.

Rangers to use Rapada as lefty specialist

MINNEAPOLIS -- Clay Rapada, a left-handed reliever who put up terrific numbers at Triple-A Oklahoma City this season, is back in the big leagues. Rapada was recalled by the Rangers as a September callup and added to their bullpen. He joins Darren Oliver, Matt Harrison and Michael Kirkman in giving the Rangers four left-handed relievers.

Rapada was 1-2 with a 1.82 ERA in 50 appearances for Oklahoma City and allowed just 32 hits and 21 walks in 59 1/3 innings, giving him the lowest WHIP for any pitcher on the team. He struck out 61 while opponents hit .158 off him. Left-handed hitters were 11-for-92 (.120) off him.

His main assignment with the Rangers will be to get out left-handed hitters.

"He's death on left-handers," manager Ron Washington said.

Rapada was signed by the Rangers as a Minor League free agent in the offseason and has pitched in 33 Major League games -- one for the Cubs and 32 for the Tigers -- with a 3-0 record and a 4.94 ERA. Left-handers are hitting .235 off him at the Major League level while right-handers are hitting .269.

Teagarden rejoins Rangers as third catcher

MINNEAPOLIS -- Catcher Taylor Teagarden rejoined the Rangers on Friday as a September callup for his third tour with the Rangers. In his previous two, he was the backup catcher. Now he is third string behind Bengie Molina and Matt Treanor and not likely to get much playing time until the Rangers clinch the division.

"I'll get him a game here or there," Rangers manager Ron Washington said. "I'm not going to have him up here sitting around. He's going to play."

The Rangers aren't planning on calling up anybody else until Triple-A Oklahoma City is done with the playoffs. At that point the Rangers might call up pitcher Doug Mathis, catcher Max Ramirez and/or infielder Chris Davis. Outfielder Willy Taveras is another possibility if the Rangers need a pinch-runner.

The Rangers did activate Dustin Nippert off the disabled list on Friday. Nippert was placed on the DL with a head contusion on July 20, a day after being struck in the head by Tigers outfielder Austin Jackson's liner in the sixth inning. He then pitched 6 1/3 shutout innings spanning three rehab games.

The Rangers are also expecting to get Scott Feldman back on the next homestand. He allowed two runs in four innings in a rehab assignment on Wednesday for Oklahoma City and will make one more start for them. He has a bone bruise in his right knee.

Rangers sign Prior to Minor League deal

MINNEAPOLIS -- Former All-Star pitcher Mark Prior, whose career has been derailed by a devastating shoulder injury, has reached an agreement with the Rangers on a Minor League contract. He will pitch at Triple-A Oklahoma City in relief, and this is considered a long-term project. He is not expected to be an option for the Rangers this season.

The right-hander signed an independent league contract with the Orange County Flyers of the Golden Baseball League on Aug. 3 and has allowed one unearned run over nine relief appearances (11 innings pitched), while compiling 22 strikeouts against 5 walks.

"I just want to see what I have left," Prior told the New York Times recently. "I'm doing this because I love playing. If what I've got left is good enough to get back up there, I'd love to put some more years under my belt. The only regret would be what if I could have one more shot, whether I get back for one day or five or six more years. I don't think I was ready to say, 'All right, that's it. I've had enough.'"

Prior was an 18-game winner for the Cubs in 2003 but hasn't pitched in the Major Leagues since '06, when he was 1-6 with a 7.21 ERA in nine starts. He has had a variety of injuries in his career, but it was a fragile shoulder that brought him down.

He was the second overall pick behind Joe Mauer in the 2001 Draft and his $10.5 million signing bonus was the largest ever given out until Stephen Strasburg signed for $15 million last year.

"We got reports he was throwing well in the independent league," manager Ron Washington said. "He might become a very good bullpen piece."

Worth noting

Darren Oliver has been dealing with a sore back but said it has been improving. ... August was the Rangers' best month ever as far as ratings on FOX Sports Southwest. ... C.J. Wilson is the Rangers' Player of the Month for August. ... Texas' bullpen had a 3.28 ERA going into Friday's game, the lowest in the American League.