Mauer came in Wednesday still feeling sore, and the decision was made to place him on the DL for the first time this season. It's also the first oblique injury for Mauer in his career.
"Leaving the park last night, I was pretty sore, so it's frustrating," Mauer said. "Hopefully, I can get back in the lineup when I'm up."
Mauer had been swinging well recently, as his two-run double extended his hitting streak to 12 games. Mauer was batting .362 with six doubles and 12 RBIs over that stretch to improve his slash line on the season to .271/.342/.353 in 76 games.
"He was swinging really good," manager Ron Gardenhire said. "He was putting in a lot of hard work and driving in some runs for us. So I'm sure he's really frustrated right now because he's been working hard to find his swing."
Colabello, who will split time at first base with Chris Parmelee and Kendrys Morales in Mauer's absence, had been hitting well recently at Rochester. In his last 29 games at Triple-A, Colabello hit .318/.392/.561 with six homers, eight doubles and 25 RBIs.
"It's been about a month now, I've been swinging the bat well," Colabello said. "There were a bunch of games in there where I didn't get many hits, but I was barreling a bunch of balls."
The DL move also officially knocks Mauer out of the All-Star Game, which will be held at Target Field on July 15. Mauer said he expects to still represent the Twins and Major League Baseball as the official ambassador for the Midsummer Classic, but he was frustrated that he won't be able to participate in the game in his hometown.
"It's disappointing," Mauer said. "Any time you have to a chance to go to an All-Star Game is an exciting time, especially in your hometown. It's tough to describe. I definitely wanted to be a part of this as a player, but I guess that's out of the question now."
Mauer was an unlikely All-Star given his uncharacteristic struggles this season and the deep competition at first base, as second baseman Brian Dozier and catcher Kurt Suzuki remain the most likely Twins position players to be named All-Stars.
Fans can cast their votes for starters at MLB.com -- online or on a mobile device -- using the 2014 All-Star Game MLB.com Ballot Sponsored by Experian until Thursday at 10:59 p.m. CT. The 2014 All-Star Game will be played at Target Field on Tuesday, July 15 on FOX.