Back issues pretty much forced Roy Oswalt out the door in Philadelphia, and the Texas Rangers were there to give him another chance.

Oswalt will make his anticipated debut Friday in the opener of a three-game series versus the Colorado Rockies at the Ballpark in Arlington. The longtime Houston Astros ace made four minor league starts for the Rangers and last toed the rubber on Sunday for Triple-A Round Rock. He also tossed a bullpen session under the watchful eye of Rangers president and Hall of Famer Nolan Ryan.

"He's ready to go," manager Ron Washington said before the Rangers' game on Wednesday against the Padres. "The reports we got say he's ready to go. That's what we brought him for, to bring him to the big leagues, and he's ready, so we made the decision to do it. We challenge him now."

The right-hander hasn't pitched in the big leagues since Game 4 of last year's NLDS versus St. Louis and is replacing Scott Feldman in the rotation, with the latter expected to move back to the bullpen. Oswalt, a three-time All-Star, has a career record of 159-93 with a 3.21 ERA. He compiled a 9-10 mark with a 3.69 ERA in 23 starts for the Phillies last season before back problems halted his production.

Texas hopes Oswalt's career success versus the Rockies will keep the club in the win column, as he is 8-2 with a 1.94 ERA in 12 starts against them. Oswalt is 2-5 with a 4.78 ERA for his career at the Ballpark in Arlington.

The Rangers have won six in a row and nine of 10 games, and sit five games in front of the LA Angels of Anaheim for AL West bragging rights. They are coming off back-to-back sweeps of Houston and San Diego, and recorded a 4-2 win over the Padres on Wednesday at Petco Park. Rangers starter Yu Darvish was on point through eight innings and gave up two runs and five hits with eight strikeouts. Joe Nathan posted his 15th save in the ninth.

"The first two innings, it looked like he was trying to find his rhythm," Rangers manager Ron Washington said. "From that point on, he wasn't going to be denied. His breaking ball came, his cutter came, he moved the ball around the zone pretty good. He did a great job."

Michael Young had an RBI and scored a run for the Rangers, who will begin a 10-game homestand Friday versus Colorado, Detroit and Oakland. Josh Hamilton went 1-for-4 with a run scored in his second game back since missing time with an intestinal virus. He is one of the main reasons why the Rangers are 12-3 against the National league this season.

Colorado will resume its nine-game road trip this evening and salvaged the finale of a three-game series at Philadelphia with Thursday's 4-1 victory.

The Rockies won for just the second time in 14 tries and can credit their pitching staff for last night's success. Jeff Francis gave up the only run of the game in five innings, while Josh Roenicke, Rex Brothers, Matt Belisle and Rafael Betancourt held the Phillies off the scoreboard the rest of the way.

Roenicke got the win and Betancourt tacked on his 11th save.

"When you sit down here right now and look at it, we were in position to win two games in this series," Tracy said of the recent series. "But it didn't happen, and now we're going to go play an awfully good baseball team."

Rockies rookie Wilin Rosario hasn't been to shabby either and homered for the second straight game on Thursday. Rosario and Chris Nelson both clubbed two- run homers for Colorado, which is 2-4 so far on the road swing. Rosario leads all rookies with 11 homers and 32 RBI. Carlos Gonzalez went 0-for-4 to have his eight-game hitting streak stopped and was batting .444 over the stretch.

The Rockies learned that All-Star shortstop Troy Tulowitzki underwent successful surgery to remove scar tissue that was built up over a nerve in his left groin area. A timetable for his return has not been set. Tulowitzki hasn't played since late May and is batting .287 with eight home runs and 27 RBI in 47 games.

"We know that he has peace of mind in knowing that what it was that he was dealing with is now fixed, and the time frame is not longer than initially anticipated after doing the tests and looking at MRIs and things like that," Tracy noted. "We're very encouraged in relation to the news that we got."

Christian Friedrich draws the start for Tracy's club against Texas' vaunted lineup and has lost consecutive starts since winning three straight. Friedrich allowed three runs -- two earned -- in five innings of a 4-1 loss at Detroit on Saturday to fall to 4-3 with a 5.60 ERA in eight starts as a rookie.

The left-hander and product of Eastern Kentucky is 3-1 in five road starts for a Rockies club that is only 2-11 against American League teams this season.

Colorado and Texas are meeting for the first time since the Rockies won two of three matchups in 2006 at Coors Field. These two clubs haven't met in the Lone Star State since 2001.