Morneau, who underwent surgery to remove a herniated disk fragment in his neck on June 29, is hitting .353 with two doubles in four rehab games with Rochester.
Morneau was originally placed on the disabled list, retroactive to June 10, with a sprained left wrist, before electing to undergo neck surgery later in the month. He was hitting .225 with four homers and 21 RBIs in 55 games before hitting the DL.
Twins manager Ron Gardenhire said Morneau is expected to play in six to eight rehab games before he makes his return.
Gardenhire also added that second baseman Alexi Casilla, who is on the disabled list with a strained right hamstring, will not need to go on a rehab assignment and is still on track to make his return on Friday.
"He'll be activated Friday if everything continues to progress, and he'll leave with us Thursday night," Gardenhire said. "And then we'll activate him on Friday in Cleveland."
Casilla was batting .259 with 15 stolen bases and a team-high 21 doubles in 96 games this season before injuring his hamstring while running the bases against the Rangers in Texas on July 27.