Colon, 44, made one start with Triple-A Rochester and was hit hard, lasting just 76 pitches over 3 2/3 innings while allowing four earned runs on four hits, including a home run on Thursday against Lehigh Valley. He struck out five.
"I'm not worried about (total) pitches," Twins manager Paul Molitor told reporters Saturday. "One of the things he's always been is durable."
Colon, who had gone to Atlanta on a one-year, $12.5 million deal in the offseason, was designated for assignment after going 2-8 with an 8.14 ERA in 13 starts for the Braves.
Last season with the Mets, Colon earned his fourth All-Star selection, going 15-8 with a 3.43 ERA in 33 starts. The Twins will be the 10th different team in 20 major league seasons for the 2005 Cy Young Award winner.
He has a career record of 235-170 with a 4.02 ERA and 2,407 strikeouts. His win total ranks third among Latin American-born pitchers, trailing only Nicaraguan Dennis Martinez (245) and fellow Dominican Juan Marichal (243).
Mauer, who was batting third against the Astros on Saturday night, last played on July 4 and was placed on the DL on July 7 with a strained lower back. Buxton left the Twins' 10-5 loss against the Houston Astros in the sixth inning on Friday with left groin soreness.
"His legs are such a huge part of his game," Molitor said of Buxton. "You don't want him to be battling that at less than 100 percent going into the last few months of the season, so we're going to take the 10 days and try to get it right."
Kennys Vargas has started at first base in Mauer's absence. He was forced out of Friday night's game in the seventh inning with a left foot contusion.
Mauer worked out before Friday's game and took part in batting practice. The 34-year-old veteran is hitting .286 with five home runs and 34 RBIs this season. The Twins enter Saturday's action in second place in the AL Central, 2.5 games behind the first-place Cleveland Indians.