As a manager with a pitcher who found himself in his own sticky situation last week, the Yankees’ Aaron Boone said Thursday there is still gray area regarding the acceptable use of rosin. 

Whereas Mets ace Max Scherzer was ejected from his start Wednesday for having excessive stickiness on his hand, which he said was from sweat and rosin, Yankees right-hander Domingo German was allowed to stay in the game last Saturday despite being warned to wash his hands and then still having some rosin on his pinky the following inning. 

Major League Baseball has been trying to crack down on the use of sticky substances this season, but there remains some question as to how much rosin is too much. 

“Yeah, there’s probably gray area,” Boone said before the Yankees’ 9-3 win over the Angels on Thursday. “It’s tough. It’s tough for everyone involved. Obviously the league’s trying to make things as level as possible and you certainly want that as a competitor. But yeah, trying to learn and have those conversations and be as proactive as you can.

“But there does seem to be some gray in there. We’ll just try to stay out in front of things as best we can.” 

Gerrit Cole declined to discuss Scherzer’s situation, not knowing the full details, but said the memo MLB sent out this spring explained that excessive use of rosin is not allowed. 

“There’s some parameters there that we’re aware of,” Cole said. “We know the umpires are looking for it. I know that it can be excessive and the umps have been trained to combat that.” 

Luis Severino (lat strain) and Harrison Bader (oblique strain) squared off in a live batting practice session Thursday afternoon as both players continued to rehab from injuries. 

Severino threw 15 pitches in the bullpen before throwing 20 more in the live session against Bader and Willie Calhoun.

The right-hander came out of it feeling “great,” he said, while Boone said Severino was hitting 95-96 mph with his fastball. 

The next step for Severino is heading to Tampa, where he will throw another live session in five days.

Boone was unsure whether Severino would be ready to go on a rehab assignment after that or if he would need two more live sessions. 

Severino will still need to build his pitch count up incrementally, meaning he may not be in play to return to the Yankees until at least mid-May. 

“But the good thing is I feel good,” Severino said. 

Bader, meanwhile, is set to begin a rehab assignment on Friday at Double-A Somerset. The center fielder is expected to need around a week of games before he is ready to rejoin the Yankees. 

Carlos Rodon will not throw “for the next couple days,” Boone said, as the Yankees try to figure out what is going on with his ailing back.

The left-hander, who was rehabbing a forearm muscle strain when the back issues arose, was set to undergo a CT scan to get more information. 

“But everything structurally with the back looks fine,” Boone said. “It does look like more of a nagging, couple-day thing.” 

Josh Donaldson (hamstring strain) underwent another MRI exam on Thursday after he experienced tightness during his rehab game Tuesday night.

While the Yankees did not immediately disclose the results, they did shut down Donaldson’s rehab assignment Thursday night, and his next step is uncertain. 

The Yankees signed veteran outfielder Kole Calhoun to a minor league contract Thursday and assigned him to the Florida Complex League.

The left-handed hitting Calhoun, 35, spent last season with the Rangers, batting .196 with 12 home runs and a .587 OPS. 

— Additional reporting by Dan Martin