The Rangers' bullpen had been one of the best in the big leagues until it flopped Thursday night against a last-place team.
Craig Tatum drew a bases-loaded walk in the eighth inning to force in the go-ahead run, Scott Moore and Felix Pie homered, and the Baltimore Orioles rallied from a four-run deficit for a 6-4 victory over Texas.
"Our bullpen's been lights-out all season long, so anytime we hand it over to those guys we feel we have a great chance to win the game," Rangers third baseman Michael Young said. "But nobody's perfect. They're going to have games where things don't bounce their way. That happened tonight."
Baltimore loaded the bases in a three-run eighth against Frank Francisco (6-4) as Nick Markakis reached on an error by shortstop Elvis Andrus, Ty Wigginton singled and Adam Jones was hit by an 0-2 pitch.
Darren Oliver relieved and hit Pie with another 0-2 pitch to force in a run and tie it at 4. Oliver then walked Tatum to force in pinch-runner Cesar Izturis, giving Baltimore a 5-4 edge.
Julio Lugo's bloop RBI single off Darren O'Day later in the inning made it 6-4.
"We've been falling behind in games, but these guys have stayed calm," Baltimore interim manager Juan Samuel said. "They know they can come back, and they proved that tonight."
Francisco failed to retire any of the three batters he faced, giving up three runs (two earned) and one hit.
Rangers relievers had thrown eight scoreless innings over the previous three games and compiled a 1.94 ERA in a span of 17 games.
Hitting two batters in the eighth on 0-2 pitches compounded the Rangers' problems.
"It's not good," manager Ron Washington said. "It ended up putting runners on the bag and pushing them closer to home plate, and then Lugo hits a dunker."
Josh Hamilton had a homer and two doubles to extend his home hitting streak to 28 games. It's the second-longest home streak in club history behind Al Oliver's 30 games in 1981.
Even with the loss, the Rangers' 50-35 record matches the 1996 team for the best 85-game start in team history.
Texas starter Tommy Hunter struck out a career-high seven over six-plus innings, allowing three runs and seven hits. But he ended up with a no-decision when the bullpen faltered.
Moore's solo homer in the fifth, Pie's leadoff shot in the seventh and Corey Patterson's RBI single off Alexi Ogando later in the seventh pulled the Orioles to 4-3.
David Hernandez (4-7) tossed 1 1-3 shutout innings for the win and Alfredo Simon got three outs for his 11th save in 13 chances.
Baltimore had lost three straight and six of seven. The Orioles improved to 10-34 on the road.
Texas took a 3-0 lead in the second against Jeremy Guthrie. Nelson Cruz and Young had RBI singles, and Cruz scored from third on Guthrie's wild pickoff throw to first.
Hamilton's 22nd homer, a solo shot in the third, extended the Rangers' advantage to 4-0.
Guthrie allowed four runs and seven hits in 4 2-3 innings. His outing ended when he walked three of his five batters in the fifth, although the Rangers were unable to take advantage against Guthrie and reliever Mark Hendrickson.
"Not to allow any runs with the bases loaded, that was the difference in the game," Guthrie said. "It was a great effort by our bullpen."
Baltimore's bullpen had an 8.05 ERA in its previous six games.
Texas stranded 11 runners, four at third base.
"We had Guthrie on the ropes, scored four runs on him but had a chance to get more and didn't come through," Washington said.
NOTES: The Rangers are expected to call up LHP Matt Harrison from Triple-A Oklahoma City to make Saturday night's start against Baltimore. Orioles manager Juan Samuel hasn't decided on a starter for Saturday night. Texas lacks a definitive fifth starter with RHP Rich Harden and LHP Derek Holland on the 15-day disabled list. Harrison might get a second start after the All-Star break if neither Harden nor Holland is ready. ... Young finished fourth behind Nick Swisher of the New York Yankees in Internet voting for the final AL All-Star spot. The Rangers will honor Young before Saturday night's game against Baltimore for becoming the franchise's career hits leader. Young surpassed Ivan Rodriguez's 1,747 hits on June 16 at Florida. ... The Orioles hadn't won in any of Pie's first 10 games before ending that drought against Texas.