Jemile Weeks had three hits, including his 3, and salvage a three-game set.
"That's the way it goes. You hope that you can sweep somebody, but sometimes that doesn't happen," Washington said about the Oakland A's who overcame a 3-1 deficit to win. "They played a pretty good game today, so you have to give them credit."
Mike Adams (1-3) came on in the eighth and allowed the go-ahead run. Weeks sliced a one-out double into the left-center gap and Coco Crisp came through with a groundball into the hole on the right side of the infield, which brought home Weeks for a 4-3 lead.
Grant Balfour (5-2) worked a 1-2-3 eighth to pick up the win for the A's, who had lost three straight and six of their past eight. Andrew Bailey saved his 21st game of the year by retiring the Rangers in order in the ninth.
Josh Hamilton, Yorvit Torrealba and Michael Young each had two hits for the Rangers as their magic number to clinch the AL West was cut to two with the Angels loss on Thursday night to Toronto, 4-3, in 12 innings.
Trevor Cahill started the game for Oakland and lasted 6 2/3 innings, while allowing three runs on 10 hits and one walk.
Colby Lewis toed the rubber for Texas as he went 6 1/3 innings, surrendering three runs on four hits and two walks, while fanning seven.
Oakland started the scoring in the home-half of the first inning. Josh Willingham shot a sharp double past the glove of third baseman Adrian Beltre, scoring Weeks on a close play at home as he slid safely past the swipe tag of Torrealba. Weeks reached on a leadoff single.
Young started the second with a looping single to center, and scored on a Beltre double to right-center field. Beltre launched a high-slicing liner to right-center field and Crisp nearly made a remarkable jumping grab as he barreled into the wall. After David Murphy moved Beltre to third on a groundout to first base, Nelson Cruz lifted a sacrifice fly to center to bring him home and make it a 2-1 game.
Hamilton poked a high flyball to left in the sixth, but Willingham lost the ball in the sun and it fell in front of him as Hamilton reached second. Two batters later, Murphy found the hole on the right side with a groundball single to plate Hamilton.
Weeks launched a solo shot to right in the Oakland sixth to cut the margin back to one, 3-2.
"Every day I got something said about me or somebody telling me something every day about the home run deal, but it's all in fun and I took it all in fun," said Weeks who needed 376 at-bats to hit his first home run. "They definitely gave me the silent treatment when I came in (dugout)."
The A's tied it up in the seventh. David DeJesus worked a one-out walk, and advanced to third on a Cliff Pennington double in the right-center field gap. Scott Sizemore, who pinch-hit for Brandon Allen, grounded out to second base to score DeJesus.
Texas goes home to play Seattle in a three-game set over the weekend, and travels to Anaheim to take on the Angels in the final three-game series of the regular season.
Oakland concludes the season 43-38 at home. The A's plays three-game sets against the Angels and Mariners on the road to finish the season...Despite the loss, Texas finished with a 13-6 mark against the A's this season, and are 34-17 against AL West opponents this year...Oakland improved to 19-25 in one- run games.