Yankees general manager Brian Cashman was in the back of the press box telling The Post what he likes best about yesterday’s starting pitcher David Phelps.

“What’s impressive to me is his composure,’’ Cashman said. “From Day 1 he’s acted like nothing is overwhelming.’’

A few minutes later in the midst of a first-inning jam, Phelps wheeled and threw to shortstop Jayson Nix to pick off Jose Bautista at second base to end the threat.

Composure can take you a long way in this game, all the way from the 440th pick of the 2008 draft to the pitching mound at Yankee Stadium. Phelps pitched a career-high seven innings yesterday in a 7-2 win over Toronto.

“That pickoff was huge,’’ Phelps said. “That could be the game right there.’’

Throw in a couple of home runs from resident superstar Robinson Cano and one from key pickup Travis Hafner, and this day offered a perfect example of how the Yankees are in first place in the AL East with a 27-16 record, while the Blue Jays — everyone’s preseason favorites — dropped to 17-26.

The Yankees have won nine of the past 12. Phelps (2-2) struck out eight and allowed only one run over those seven innings, his first win as a starter this season.

Phelps, 26, told The Post this season means so much to the young Yankees who have come up through the system because they are getting the chance to prove themselves. He mentioned catcher Austin Romine, third baseman David Adams and pitchers Adam Warren, Vidal Nuno, Preston Claiborne and Dellin Betances. Phelps, Adams and Claiborne all played together as far back as the Cape Cod League.

“I’m really excited to look around this locker room and see all these guys,’’ Phelps said. “We all feed off each other. The better that we do, the more doors will be opened for guys that we played with as well. It’s been a blast this year.’’

When he was picked in that 14th round of the 2008 draft, did Phelps ever envision a day like yesterday?

“I didn’t worry about where I was picked because my sophomore year at Notre Dame was outstanding, and my junior year I didn’t pitch as well so I knew I was capable of getting guys out,’’ Phelps said. “And I was fortunate enough to get in with the Yankees and a lot of great minds and great coaches really helped me. I thank God every day that I’m part of this organization.’’

When Cashman meets with those minor leaguers, this is what he tells them: “My job is find someone better than you, so make sure you don’t let me do that. It’s not about me messing with you, it’s about you understanding the situation. You could be an All-Star in your league but my job is to find someone better than you.