"[Kurt] Suzuki's not playing today," the skipper said before the rubber match of his team's three-game set against Detroit. "If he's not playing, he can't be in that spot. So that's the only reason Ryan is there."
Still, it's no secret Sweeney's left-handed bat is deserving of the move up in the lineup.
The A's outfielder entered Sunday's contest batting .333 (16-for-48) with seven extra-base hits over his last 13 games after collecting just 10 extra-base hits over his previous 57 games.
"He hasn't made any drastic changes," Geren offered. "Guys have hot streaks and cold streaks. One of the things I say about a lot of hitters who are swinging the bat well is they're able to use the whole field. Ryan's doing that.
"Some try to do too much in one direction, but if you're spreading your hits out, that makes you tough to pitch to."
Sweeney's success against the Tigers makes him all the more attractive to his manager, as he entered Sunday with a .333 career mark against Detroit. This season, the 24-year-old was 12-for-32 (.375) with a home run and four RBIs in eight games when facing the Tigers, prior to Sunday's game.
"He's been swinging the bat pretty well," Geren said. "He's had a lot of success against Detroit, so we'll see what he can do today."
With Sweeney in the three-hole, the left-handed-hitting Jack Cust was also moved up in the batting order to No. 5 after spending the past week hitting seventh.
"He moved up because Sweeney moved up," Geren said with a laugh. "It's kind of a domino effect. Plus, it diversifies the lineup and allows us to switch up the lefties and righties."
Cust entered the game 3-for-6 with an RBI and two walks in the series and 6-for-16 with two RBIs and five walks in the first eight games of a nine-game homestand.
Jane Lee is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.