Baker gave up eight runs and 12 hits in 2 2/3 innings of Minnesota's 10-3 split-squad loss to the Tampa Bay Rays on Wednesday.
After breezing through his previous five appearances of the spring, it's not the kind of performance he was hoping for with the opener less than a week away.
"It wasn't the last start that I wanted," Baker said. "I feel like I battled and never gave in. Sometimes you have days like that."
Baker only gave up three earned runs total in his previous five outings of the spring and carried a 1.40 ERA into this start. He will pitch in Anaheim against the Los Angeles Angels on April 5, having finished the spring 3-1 with a 4.50 ERA.
"I feel good. I'm healthy," Baker said. "I feel like the ball's still coming good out of my hand. Obviously we're not robots so sometimes you're going to struggle a little bit."
Ben Zobrist went 3 for 3 with two doubles and four RBIs for the Rays, who won their 19th game of the exhibition season. That's a franchise record, one better than 2008 when they made the World Series.
Rays starter Wade Davis allowed two runs on four hits and struck out five in six innings.
Zobrist had another two-run double in the second inning, and the Rays chased Baker with a four-run third that made it 8-2. Rodriguez, who had three hits, added an RBI double.
"He got his work in, let's put it that way," manager Ron Gardenhire said of Baker, using one of his favorite sayings when things do not go well. "You can sugarcoat it anyway you want to. ... We're not taking too much more out of this performance."
Twins slugger Justin Morneau went 0 for 4 and watched his spring training average fall to .156. He missed the last three weeks of last season with a back injury and has been easing his way through spring training so far this year.
Morneau has cut down on the amount of swings he takes per day, but has been slow to get going with the lighter workout regimen.
"He's just fighting himself a little bit right now," Gardenhire said.
Hank Blalock also has had a tough spring. He signed a minor league contract with the Rays earlier this month in hopes of giving his injury plagued career a jump-start. But he went 0 for 2 with a strikeout on Wednesday, dropping his average to .194.
There is a provision in the minor league contract he signed with Tampa Bay that would allow him to opt out and seek a job with another team if he doesn't make the 25-man roster.
Rays RHP Rafael Soriano allowed one run on two hits and struck out one in an inning of a Triple-A game against the Orioles. ... The Rays reassigned C Alvin Colina and INF Joe Dillon to minor league camp. ... The Twins optioned C Wilson Ramos and LHP Glen Perkins to Triple-A Rochester and placed RHP Joe Nathan (elbow) and C Jose Morales (wrist) on the 15-day disabled list.