The first day of Jordan Montgomery’s big-league life was a mixed bag filled with nerves, thrills, strikeouts and too many pitches.

The 24-year-old lefty arrived from Triple-A last Wednesday and stepped into the Yankees’ No. 5 starter role against the Rays at Yankee Stadium. He was charged with three runs (two earned), allowed five hits and struck out seven, the second most by a Yankees lefty in his major-league debut since 1913.

But Montgomery lasted only 4 2⁄3 innings, getting pulled after throwing 89 pitches in the 8-4 victory. So the goal for his second start Monday night against the visiting White Sox is clear.

“I just want to go deeper,” Montgomery said before Sunday night’s game against the Cardinals. “Really, my job out there is to do what the team needs to win. So I’m going to just keep trying to do that.”

The South Carolina alum isn’t a power pitcher, but he’s 6-6 and brings some overhand deception in his delivery.

“I think fastball command needs to improve for him,” Joe Girardi said. “But I’m not surprised that it wasn’t great for him considering it was the first day he ever pitched in the big leagues. I think his slider will be better. I think that’s a big pitch for him.”

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Michael Pineda has pitched in with advice to the rookie. The main message? “Not to be content with where you are now,” Montgomery said. “Keep working so you can stay here.”

Extra bases

Matt Holliday didn’t start after being scratched Saturday with lower-back stiffness. He took batting practice, and Girardi said he was “much better.” . . . Chase Headley went 2-for-2 with two walks. He has a .410/.531/.615 slash line and leads the majors with 26 times on base (16 hits, 10 walks). “I just think he’s using his legs more,” Girardi said . . . Ronald Torreyes’ two-run double gave him a team-high 10 RBIs in only 40 at-bats.