The Yankees are planning to begin the regular season without Frankie Montas in the rotation, as the right-hander continues to battle inflammation in his pitching shoulder.

Montas is eight to 10 weeks behind in his offseason training and could miss the first month of the regular season, according to a report by the New York Post. Montas, who turns 30 in March, agreed to a $7.5 million contract on Friday, avoiding arbitration.

“The biggest thing with Frankie is getting him right and well,” Yankees manager Aaron Boone told the YES Network on Thursday. “We feel like when we have that, we’ve got another frontline pitcher, but he’s probably going to be a little bit behind.”

Montas dealt with a similar issue last season with the Athletics and Yankees. He was forced to exit from a July 3 start with Oakland and missed nearly three weeks, though he pitched well in two starts preceding an Aug. 2 trade that shipped pitchers Luis Medina, JP Sears, Ken Waldichuk and infielder Cooper Bowman from New York to the A’s in exchange for Montas and right-hander Lou Trivino.

Montas went 1-3 with a 6.35 ERA in eight regular-season starts for the Yankees, the last of which came on Sept. 16 at Milwaukee, when the shoulder issue flared up again. He returned to pitch one inning in the American League Championship Series against the Astros, at which time the club said they expected Montas to make a full recovery before Spring Training.

“We haven’t had a chance to see the real deal yet from him,” general manager Brian Cashman said in December.

Boone had slated Montas in his probable starting rotation behind Gerrit Cole, Carlos Rodón, Luis Severino and Nestor Cortes. Montas’ injury could create a spring competition between Domingo Germán and Clarke Schmidt for the No. 5 spot.

“Hopefully if everything goes well where he starts throwing in the next couple of days, we’re in January, [so] that’s a pretty long on-ramp to put him into position,” Boone said. “We’re going to play it conservatively because he’s had this lingering nuisance going on for the last half of the year. We want to be smart with it, conservative with it, [and] make sure he’s in a really good spot [so] that when he does join the rotation, he’s flying.”