He now has a 3.77 ERA in five starts since he rejoined the rotation and has pitched at least six innings in each of those outings.
"I'm feeling more comfortable," said Duensing, who improved to 3-8 with a 4.46 ERA. "I've thrown more strikes down in the zone for the most part. I've had a couple shaky innings here and there, but I thought tonight I was able to make some good pitches in key situations. We're starting to put some things together and hopefully we'll keep it going."
Duensing, making his ninth start of the year, allowed two runs (one earned) on five hits and a walk over six innings. He also struck out a season-high seven batters, which was his highest total since striking out nine against the Indians on Aug. 13, 2011.
"We just want him to take the ball and give us a chance to win a game and that's what he did," Twins manager Ron Gardenhire said. "When he starts trying to pump the ball up to 93-94 mph he gets himself in trouble. He stayed within himself, he used his changeup, used his slow breaking ball and he moved the ball in and out. That's how he has to pitch."
Duensing was staked an early lead by the Twins, who scored two runs in the first against right-hander Brandon McCarthy. Josh Willingham brought home the first run against his former team with an RBI double before Trevor Plouffe walked with the bases loaded.
Minnesota added two more runs in the second when Darin Mastroianni and Willingham both provided RBI singles.
The A's got on the board in the bottom of the inning on an RBI double from Josh Donaldson to score Yoenis Cespedes.
Oakland scored again in the third and was helped by a throwing error from Pedro Florimon on a grounder hit by Coco Crisp. Crisp later scored on an RBI groundout after stealing second base and reaching third on an errant throw from catcher Joe Mauer.
But the Twins scored twice in the fourth on a two-run single from Mauer to score Florimon and Ben Revere, who both singled and advanced on a sacrifice bunt from Mastroianni.
"It was a mess, from beginning to end," said McCarthy, who gave up six runs on 10 hits and a walk to fall to 6-5 with a 3.16 ERA. "I just mechanically felt completely out of whack with everything. That's pretty much what showed. I was horrible in the bullpen and had nothing at any point. It's been a long time since I had a day like this, where you just want a rewind button in the first inning and start all over."
Florimon, who went 3-for-3 with a walk, sparked another rally in the eighth against reliever Travis Blackley, reaching on a leadoff single and later scoring on a sac fly from Mastroianni.
"He's been pretty good," Gardenhire said of Florimon, who is 6-for-12 with two walks since being called up from Triple-A Rochester last week. "He's been running around real nice, giving us good at-bats, some nice swings. I'm kind of fond of the defense. I like to see the defense. He made that high throw today. ... He's got to get rid of it a little quicker. But he's calmed that position down out there. Plus, he's put out some really nice swings."