"We weren't necessarily looking to add any left-hander, it had to be the right guy," Rangers general manager Jon Daniels said. "We felt Mike was above the line. He has pitched in meaningful spots, he has pitched in the AL East and he has closed for some clubs. We've got good reports about him and felt it was a chance to help our club."
Gonzalez is expected to join the Rangers on Thursday. He gives them a second left-hander in the bullpen along with Darren Oliver. The trade was completed on Tuesday night.
"It's kind of a mixed reaction for me right now," Gonzalez said. "I'm excited. I'm going to go out there and I'm going to try to win the championship now, and especially right now that I'm feeling good. The bad part is obviously I wanted to do more here in Baltimore."
The Orioles signed Gonzalez to a two-year, $12 million contract before the 2010 season. But he missed three months last year because of a strained left shoulder. From 2004-09, he was one of the premier left-handed relievers in the National League while with the Pirates and the Braves.
Over those six years, he was 14-16 with a 2.41 ERA while holding opponents to a .209 batting average. Left-handed hitters batted .201 off him, and he also had 54 saves with a career high of 24 with the Pirates in 2006.
"Gonzo is going to be a really nice piece for Ron Washington and the Rangers," Orioles manager Buck Showalter said. "He's pitching as good as any American League reliever, left-hander reliever period. They're catching him at a great time. He's familiar with the American League, so there should be little transition."
Strop is 4-4 with a 3.59 ERA and 11 saves in 39 games at Round Rock. He was 0-1 with a 3.72 ERA in 11 games for the Rangers earlier this season.
Treanor was one of the Rangers' catchers on their run to the World Series last season. He re-signed with Texas in the offseason, but was traded to the Royals toward the end of Spring Training. He returns as the Rangers' third catcher for September.
"There was a chance to get him and he's a good fit in our clubhouse," Daniels said. "He knows the guys on our staff and he knows the American League. It's a good fit for us."
Washington said that Yorvit Torrealba and Mike Napoli will continue to be his primary catchers. He had been using both at designated hitter lately, and Torrealba was the DH on Wednesday night against the Rays.
But that arrangement is likely to end when Adrian Beltre comes off the disabled list on Thursday. Beltre will go back to third base and Michael Young will resume his old duties as the full-time DH. Treanor will likely catch only occasionally. He was C.J. Wilson's primary catcher at the end of last season and into the playoffs.
Treanor, 35, played in 65 games for the Royals and was hitting .226 with three home runs and 21 RBIs. He has been sidelined for a month because of a concussion sustained in a home-plate collision on July 30. But he has played seven games on a rehabilitation assignment at Double-A and has been cleared to play in the Major Leagues.
"MLB has strict requirements to be cleared, and he has cleared it," Daniels said.
Treanor is also expected to report to the Rangers on Thursday when the rosters are expanded. Both players will be eligible for the postseason roster since they were officially acquired before Wednesday's deadline.
Taylor Teagarden has been used as a third catcher by the Rangers at different points during the season. He was optioned to Triple-A Round Rock on Aug. 24 and is not eligible to return until Saturday. But he will likely remain with Round Rock through the Pacific Coast League playoffs anyway.
Daniels said the Rangers did talk to other clubs about a right-handed-hitting outfielder while Nelson Cruz is on the DL. Four of the Rangers five outfielders are all left-handed hitters: Josh Hamilton, David Murphy, Endy Chavez and Leonys Martin.
"I know we're left-handed in the outfield and right-handed in the infield," Daniels said. "But you can't manufacture something that is not there. It's something that we'll continue to keep an eye on. Right now I expect the group we have is the group we go with."