The Twins had a late rally, tying the game against the A's and bringing it into extra innings; but Oakland came out on top with a 3-2 win Saturday.
The Twins had solid pitching from starter Phil Hughes who allowed only one run.
The A's homer was a solo shot in the seventh from Oakland's Billy Butler.
MLB.com reports Hughes has allowed the most homers in the league this season at 23, and 10 were solo shots.
The Star Tribune reports Hughes thew first-pitch strikes to the first 19 batters.
Mauer rallied the Twins to tie the game 1-1 in the ninth inning. His double brought Brian Dozier home.
Miguel Sano added an RBI in the ninth with a sac fly, allowing Shane Robinson to bring in the run.
Oakland hit a run off of Twins' closer Glen Perkins, tying the game 2-2 and bringing it into extra innings. Perkins converted each of the past 29 save opportunities, but the streak came to an end, MLB.com notes.
The Twins put Casey Fien on the mound in the 10th, but he couldn't retire batter. Oakland's Stephen Vogt had the winning RBI single.
Saturday also marked Torii Hunter's 40th birthday. His teammates gave him some gag gifts to celebrate.
The Twins are now 50 - 41. They head into Sunday's game tied in the three-game series. The Twins shutout the A's Friday.
Game starts at 3:05 p.m. Sunday with Tommy Milone starting for the Twins against his former team.
With the loss, the Twins now trail the Royals by five games.