BOSTON -- A couple of hours before the start of Saturday’s game against the Rays, the Red Sox scratched star slugger J.D. Martinez due to back spasms.

Martinez is listed as day to day.

The right-handed-hitting masher has been Boston’s best all-around hitter this season, slashing .340/.423/.526 with four homers and 13 RBIs.

Steve Pearce, who has started the season in a hitting slump, replaced Martinez as the designated hitter in the 2-1 loss to Tampa Bay.

"When he got here, [Martinez] felt it was tight and he tried to go to the cage and tried to swing and it didn't make sense to push him to go back out there," Red Sox manager Alex Cora said of Martinez's after the game.

Will Martinez be available to start Sunday? "[We'll see] when he comes in," Cora said. "He got treatment the whole day, so we'll see how he feels [Sunday]."

Rehab updates

The Red Sox have missed the versatility of Brian Johnson in the bullpen, not to mention the fact he is their only lefty reliever.

There is good news on that front: Johnson is making progress from the elbow inflammation that has sidelined him since April 6, and he is likely to throw a side session on Sunday.

It will mark the first time Johnson has thrown off a mound since going on the injured list. Johnson will throw all fastballs.

The Red Sox also have three other players on the IL who are making progress.

Super-utility man Brock Holt started a Minor League rehab assignment for Triple-A Pawtucket on Friday and went 1-for-3 and walked three times while serving as the DH. Pawtucket was rained out on Saturday, but Holt will resume action on Sunday and start to mix in different defensive positions.

Holt has been out since April 6 with a scratched cornea in his right eye.

“He got what, six at-bats, that was pretty solid,” said Cora. “He said he saw the ball well, I guess they already canceled the game today. Weather’s going to be a factor I guess here and everywhere in the Northeast. It was only six at-bats, he didn’t play the field, he was the DH, but he felt good. He saw the ball a lot, he walked twice, got a hit, seems like everybody yesterday got a hit down there. So, for yesterday it was good.”

Eduardo Núñez (mid-back strain) and Dustin Pedroia (left knee irritation) both had productive workouts before the game.

Cora said the team would huddle with Nunez and Pedroia on Sunday to map out their next steps and perhaps potential dates for rehab assignments.