Cust hit a game-tying, two-run homer in the fifth inning and added a sacrifice fly in the sixth that snapped an Oakland-record string of 11 consecutive games without scoring more than three runs.
That hardly rattled the resurgent Rangers, though. Texas took advantage of all kinds of sloppiness by the hosts in the seventh inning to turn a one-run game into an 11-4 rout that pinned the A's with their season-high ninth consecutive setback.
How bad was it? A's radio play-by-play man Ken Korach, who isn't a blatant homer but isn't above putting a little Vaseline on the lens from time to time, either, probably put it best.
"In a season that's gone south very quickly for the A's," Korach told his audience in the eighth inning, "tonight might be the ugliest night."
And while A's manager Bob Geren continued to reach for positives after his club fell to 0-6 since the All-Star break, another Oakland record, his players tended to side with Korach's point of view.
"Without a doubt, this is the absolute low point of the season," second baseman Mark Ellis said.
"There's a lot of things to eat right now," added righty starter Chad Gaudin, who walked a career-high six batters and fell to 2-4 with a 5.18 ERA over his past seven assignments. "It's tough to deal with."
Rangers manager Ron Washington, Oakland's longtime infield coach before signing with Texas in the offseason, knows the feeling. His club, which has won 18 of its past 28 games, was 23-42 to open the season, Washington's first as a big-league skipper.
"We've been there, where nothing seems to go right," Washington said. "You get back in the game, and then you get out of it. You hit balls hard, and guys are standing there. Plays you normally make, you don't make."
All of the above happened to the A's on Tuesday. They trailed by a run through three innings and tied it on Kurt Suzuki's sacrifice fly in the fourth; they trailed 3-1 before Cust delivered his 16th home run of the season; and they just missed taking a 7-5 lead when Cust's moonshot with the bases loaded and one out in the sixth fell into right fielder Marlon Byrd's glove at the warning track, a potential grand slam turned sacrifice fly.
"We swung the bats a little better tonight," Ellis said, "but we still didn't play good enough to win."
Particularly in the seventh, when the Rangers broke it open with five runs on four singles, two walks and two errors.
Recently acquired righty Andrew Brown started the frame for Oakland and was greeted by a single by Byrd, who promptly stole second base and took third on a single by Frank Catalanotto. After an infield single by former A's farmhand Gerald Laird scored Byrd and chased Brown, lefty Joe Kennedy came on and committed the error that all but ended the game.
Trying to nail the lead runner at third base on a sacrifice bunt by Ramon Vazquez, Kennedy fired wide and into foul ground. Two runs scored on the play, and after a pair of groundouts, Michael Young (5-for-5, two doubles) stroked an RBI single, Kennedy walked Mark Teixeira and Sammy Sosa and Young scored on an error by shortstop Bobby Crosby.
"To play as poorly as we are right now," Ellis said, "I'm definitely surprised."
Texas tacked on another run in the top of eighth, and the A's went quietly in their halves of the final two frames.
"It was a pretty good baseball game -- for the first half, anyway," Geren said. "We let the game get away in that one inning, and we couldn't get it stopped after that."
"We're just struggling right now," Gaudin said. "Nobody's hanging their heads. Everybody's going out there fighting every day. Things just aren't going our way."
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.