ATLANTA — Washington Nationals pitcher Stephen Strasburg may have irritated a nerve in his right arm using an electrical stimulation machine.

The machines are used by athletes to build strength and are attached with adhesive electrodes. Manager Davey Johnson said the device could have been placed too close to a nerve in Strasburg’s pitching arm, leading to discomfort in Monday night’s start against the Atlanta Braves.

Johnson said the Nationals do not expect Strasburg to have continued problems with the irritated nerve, but it is too early to determine whether Strasburg will make his next scheduled start Saturday at Pittsburgh. The manager said wants to see how the right-hander throws in a bullpen session.

“I think it will settle down by the time he throws his side,” Johnson said. “I think Strasburg feels a lot better about it. So do I.”

Strasburg frequently shook his right arm while pitching six innings and allowing two runs in the Nationals’ 3-2 loss Monday night.

Yankees

Youkilis on DL with sprained back: Kevin Youkilis joined Derek Jeter, Alex Rodriguez, Mark Teixeira and Curtis Granderson on the New York Yankees’ disabled list Tuesday because of a lumbar spine sprain.

Despite a history of back trouble, Youkilis was signed to fill in for Rodriguez after the All-Star third baseman had offseason hip surgery.

Youkilis got off to a solid start, also filling in at first base, but was injured April 20 at Toronto and missed six straight games with back stiffness before going 0-for-3 with a walk Saturday.

By playing last weekend, New York lost the chance to backdate the move to April 21 and could make it only retroactive to Sunday.

Red Sox

Hanrahan activated: Boston reliever Joel Hanrahan was activated from the 15-day disabled list by the Red Sox after two weeks out because of a sore right hamstring.

Hanrahan is 0-1 with three saves and an 11.57 ERA in six appearances.

Hanrahan will serve as setup man to right-hander Andrew Bailey, who has saved five games in six chances since Hanrahan went on the DL. Bailey is 1-0 with a 1.46 ERA in 13 games.

Marlins

Stanton expected to miss about a month: In Miami, Marlins slugger Giancarlo Stanton expects to be sidelined for about a month because of a strained right hamstring.

Stanton underwent an MRI exam Tuesday and said the diagnosis was a grade-two strain on the one-to-three scale for the injury. He was hurt trying to beat out a grounder in Monday’s 15-inning victory over the New York Mets, and was placed on the 15-day disabled list.

The injury occurred just as last year’s NL slugging leader showed signs of emerging from a prolonged slump to start the season. He hit his first home run Saturday and two more Sunday.

Last year, Stanton hit 37 home runs despite missing 39 games because of injuries.

Rays

MLB looks into verbal spat between Price, UMPIRE: Tampa Bay Rays pitcher David Price is not concerned about potential discipline from Major League Baseball after his verbal spat with umpire Tom Hallion last weekend.

Price accused Hallion of directing a profanity toward him during the Rays’ 8-3 win over the White Sox on Sunday. The AL Cy Young Award winner thought Hallion missed a pitch and exchanged words with the plate umpire while heading to the dugout after the seventh inning.

After the game, Hallion vehemently denied Price’s claim.

“I’ll come right out bluntly and say he’s a liar,” he said.

Price took to Twitter to dispute Hallion’s version of events and said before Tuesday night’s game in Kansas City that he was upset with himself and never looked up until he heard Hallion’s voice.

“You can’t talk to me that way, period,” Price said. “That was my whole thing. It had nothing to do with the strike zone. You don’t talk to people that way.”