When Masahiro Tanaka takes the Yankee Stadium mound on Sunday, it will mark the start of 2015 for the Yankees.

Out since July 8 due to a small tear in the right UCL, Tanaka will start against the Blue Jays — if a bullpen session either Wednesday or Thursday doesn’t produce a physical problem for the $175 million investment who had 12 wins before getting hurt and was in contention for the AL Cy Young and Rookie of the Year awards.

“Let him do his bullpen and see what we got,’’ Joe Girardi said of Tanaka, who informed the Yankees there were no problems following a 65-pitch simulated game Monday. “Seventy to 75 pitches on Sunday and see how he does.’’

When the 25-year-old Tanaka went down, the Yankees were four games behind the Orioles in the AL East race and definitely had the look of a team that would stay in that hunt. After losing 6-1 to the Rays Tuesday night, the Yankees are 76-74, eliminated from the AL East chase and are all but mathematically eliminated from the battle for the final AL wild-card spot.

“I think that it’s all we have been waiting to get back to,’’ Girardi said about seeing Tanaka on the mound again. “He has worked very hard at it and we will see how he holds up.’’

When Tanaka was diagnosed with the tear, the Yankees opted for a rehab program instead of immediately sending their ace for Tommy John surgery. While the rehab program has put Tanaka in line to start a big league game, there is no guarantee the ligament won’t blow and require surgery at some point.