Morneau, who is on the DL retroactive to May 1 with a sore left wrist, will be returning on the first day he's eligible. First baseman Chris Parmelee was optioned to Triple-A Rochester to make room for Morneau on the roster.
"He's ready to play," Gardenhire said of Morneau after the Twins' 5-0 loss to the Indians on Tuesday. "He doesn't feel anything right now. He's swinging good. He took early BP today without any problems."
Morneau is also slated to make his return as a first baseman, as he told Gardenhire he feels more comfortable there than he does as the designated hitter. He's played just four games at first this season while seeing action at DH in 16 games.
"He said he'd rather play first base and get right back into it," Gardenhire said. "He thinks it's going to help him stay looser and into the game."
Parmelee, meanwhile, hit just .179 with no homers and three RBIs in 27 games. The Twins are hoping he can get his swing back after he hit .355 with four homers in 21 games as a September callup last season.
"He needs to go down and get his swing going," Gardenhire said. "He was with [hitting coach Tom] Brunansky last year, so he'll be back with him and hopefully he can figure some things out. Maybe that'll help his confidence a little bit."
Parmelee, 24, took the demotion in stride, saying he's eager to work on his swing in his first stint in Triple-A, as he skipped that level on the way to the Majors last year.
"I'm looking forward to going down and playing," Parmelee said. "I'm going to work on some stuff with Bruno down there, and hopefully I'll be back up here real soon."