TAMPA, Fla. -- The Yankees will be without two of their most prominent sluggers to begin the season. Aaron Judge and Giancarlo Stanton are both considered unlikely to appear in the Yankees’ Opening Day lineup, general manager Brian Cashman said on Tuesday at George M. Steinbrenner Field.

Judge is continuing to undergo a battery of tests to determine the cause of the discomfort in his right pectoral muscle, and though Cashman said that Judge has been responding well to treatment over the last 48 hours, there has been no diagnosis or set date for him to resume on-field activities. The Yankees are scheduled to open the regular season on March 26 at Baltimore.

“I don't see him ready by Opening Day because of the time frame,” Cashman said. “It’s 3 1/2 weeks, and just then the healing and then having to have a Spring Training.”

Stanton is recovering from a Grade 1 right calf strain sustained while performing defensive drills on Feb. 25. Cashman said that he believes Stanton will be ready to play sometime in April, setting the recovery time at four to six weeks from the date of injury.

“My gut would be that he wouldn't be ready by Opening Day; doesn't mean I'm right,” Cashman said. “I would say it's better to assume he won't be ready. Will he be, in theory, ready in April? At some point the answer should be yes. But Opening Day in late March, I'd say more likely than not.”

Judge was one of the earliest-arriving Yankees players, checking into the club’s Minor League complex in late January, but halted hitting and throwing after experiencing soreness in his right shoulder. Judge recently increased his throwing to 120 feet and hit indoors against coaches, but then reported discomfort in his pectoral area.

After undergoing testing during Monday’s off-day, Judge was scheduled for two more tests on Tuesday in the Tampa area. Cashman said that all exams thus far -- including MRIs -- have been negative.

"He wants to play," Yankees manager Aaron Boone said of Judge. "I think these last few days have been him just kind of grinding through, trying to get a lot of treatment. He's doing a lot of work, working out still and going through all these tests and everything. They've been busy days for him as he just tries to get back and get answers."

Neither Judge nor Stanton are currently performing any type of baseball activities, according to Boone. With Judge and Stanton unlikely to be active on March 26, the Yanks' Opening Day outfield projects to feature Clint Frazier, Mike Tauchman and perhaps Miguel Andújar flanking Brett Gardner.

“I will pick the best from the available players that are here competing, and hopefully we stay healthy in other categories, too,” Cashman said. “We certainly have a number of different people that are more than capable. Hopefully we’ve got all those choices in play by the time we're putting lineups together.”

The Yankees set a Major League record by having 30 players serve 39 stints on the injured list last season, and they have been hit early again this spring.

In addition to Judge and Stanton, right-hander Luis Severino was lost for the year to Tommy John surgery and left-hander James Paxton is out until at least May after undergoing back surgery, with outfielder Aaron Hicks out until at least June while he recovers from Tommy John surgery.

“Part of a season is the constant ebbs and flows of dealing with injuries,” Cashman said. “Right now, none of the games count while we're missing important players, so I'd rather be dealing with it right now than having it bleed deep in or cause significant time in-season. Hopefully in the case of Stanton and Judge, you're dealing with limited time rather than maximum time like with Severino.”