The Twins cut their magic number for clinching the division to six. Minnesota began the day with a nine-game lead over second-place Chicago.
"You see all these situations coming up in the minor leagues," Valencia said. "Obviously everything is magnified up here, but it's still the same game and you've just got to go with it."
Slowey (13-6) set a career high for wins, giving up two runs and five hits in 6 2/3 innings. Matt Capps earned his 40th save and 13th in 15 chances since coming to Minnesota.
Landon Powell homered and doubled for Oakland. Rookie Chris Carter kept struggling, going 0 for 2 with a pair of strikeouts -- he is 0 for 29 with 13 whiffs since making his major league debut this season.
Carter also came up short on a line drive hit down the left-field line which led to the Twins' first run in the fifth.
"It's a ball that I think he'd catch more often than he wouldn't," Athletics manager Bob Geren said. "If he had to do it again, I think he'd catch that eight or nine out of 10 times. He just didn't catch that one."
A stark contrast to Carter, Valencia has been right in the middle of the Twins ascension during his rookie year. Since arriving at the start of June, Valencia has hit .340 with 33 RBI and taken control of third base, a rotating spot for Minnesota the past several seasons.
"I've been more impressed with his defense than any other part of his game because he's worked really hard at catching the ball," Twins manager Ron Gardenhire said. "And he knows how much that means to us. I thought he had a heck of a spring for us in the short time he was there. And he's probably going above what we thought he would do his first year up here. He's really playing well."
Dallas Braden (9-13) went six innings for Oakland, allowing four runs on eight hits and four walks.
Valencia connected for the second straight game, his fourth home run this season snapping a 1-all tie in the sixth.
The Twins have seen Valencia deliver in the clutch as he's hit .431 with runners in scoring position. He's done damage at Target Field, hitting .456 for the best home batting average in the majors.
"You want to come out, being a first-year guy, and you want to perform," Valencia said. "Luckily, I've caught a bunch of breaks since I've been here. Things couldn't have gone much better for me than they are right now."
Slowey, meanwhile, is trying to put himself in position for a potential starting spot in the playoffs.
Since a trip to the disabled list with a right triceps strain at the end of August, Slowey is 2-0 and has allowed four earned runs over 15 2/3 innings in his last three starts.
Slowey gave up just one hit -- Powell's solo home run in the second -- through the first four innings.
"I think part of it is just time," Slowey said. "Time and repetition coming back from the DL and starting to trust your stuff a little bit more."
Braden, who had allowed just five earned runs over his last five road starts, cruised before the Twins scored in the fifth to tie it.
"I'm 20 innings past my career max at any level," Braden said. "This is uncharted territory as far as what my body feels like and how to maintain and bounce back. But that's something you learn and benefit from, going through these ups and downs at this point of the season."
- Minnesota CF Denard Span missed his second straight game with what is classified as a bruised rotator cuff in his right shoulder, an injury that occurred in Thursday's finale in Chicago while diving for a sinking line drive. Span said he felt better Saturday after receiving treatment on the shoulder and was available for defense or pinch-running duties. He was unsure when he would return to the lineup full-time.
- Geren said 3B Kevin Kouzmanoff is improving, but is still considered day to day. Kouzmanoff has been out since Sept. 6 with back spasms.
- Gardenhire said there is a "good chance" that Scott Baker starts on Tuesday to give the rest of the team's starters and extra day of rest. Baker threw a successful bullpen session before the game.
- Ben Revere got his first career RBI with a groundout in the fifth, scoring J.J. Hardy.