Morneau left Tuesday's game in Detroit and didn't play Wednesday and Thursday. He took early batting practice Friday and told manager Ron Gardenhire he was ready to play.
Gardenhire said the stiffness isn't related to the back injury that forced Morneau out of the lineup late last season. He didn't play after Sept. 12, missing the Twins' run to the AL Central title and the playoffs.
The 2006 AL MVP is third in the league with a .352 batting average. Prior to Tuesday's game, in which he struck out in all three at-bats against Justin Verlander, he had reached base in each of Minnesota's first 19 games.