Mauer is set to see his first action at first base, while Morneau is slated to serve as the designated hitter. Twins manager Ron Gardenhire said Mauer and Morneau will likely bat every inning to get more reps at the plate.
So far in Grapefruit League action, Mauer is 3-for-5 with two RBIs, and Morneau is 1-for-5 with an RBI.
"Surprisingly, I'm feeling pretty good at the plate," Mauer said. "But it's only a few at-bats. I've been able to square a couple balls up. That's kind of the goal early on here."
Right-hander Nick Blackburn is also scheduled to start in the "B" game against the Red Sox. He's yet to pitch in a Grapefruit League game, but he tossed a scoreless inning in last week's "B" game against Boston.