TORONTO — CC Sabathia has pitched 559 regular-season big league games and has started all of them. Of the 24 postseason games he has worked, the veteran lefty has started 23.

Yet, it is likely at some point in the final days of this regular season, Sabathia will enter a game from the bullpen.

Aaron Boone said Friday that Sabathia’s next outing — possibly Wednesday, with Domingo German following him again, as in the second game of the doubleheader in Detroit on Thursday — could be followed by the soon-to-be-retired lefty entering a game as a reliever.

“I would expect potentially a different role moving forward in the final week or so in the season when you could see him out of the pen a little bit,’’ Boone said before the Yankees’ 6-5, 12-inning loss to the Blue Jays on Friday night at Rogers Centre. “His situation will probably be a little bit fluid.’’

Sabathia pitched 3 ¹/₃ innings Thursday and gave up two runs and three hits. He walked one and fanned five in his first outing since Aug. 30 because of an inflamed right knee.

“He came through really well,’’ Boone said of Sabathia. “Encouraged by his outing.’’

Given his preference, Luis Severino would take starting over working in relief in the postseason. Nevertheless, the right-hander — who will make his season debut Tuesday night against the Angels at Yankee Stadium as a starter — is looking to help the Yankees in any role.

“Of course,’’ Severino said Friday when asked if he would like to start in the postseason. “But I want to help the team.’’

Severino opened the season on the IL with an inflamed right rotator cuff and developed a lat strain while working his way back from that.

“It happened and you can’t do nothing about it,’’ Severino said.

Considering Severino was 33-14 with a 3.18 ERA in 63 games (all starts) in 2017 and 2018, Boone is looking forward to having him back.

“The last couple of years he has been in the Cy Young conversation,’’ Boone said of Severino, who finished third in 2017 and ninth in 2018 for the Cy Young voting.