CLEARWATER, Fla. -- Justus Sheffield pounded his glove before he walked off the field. Not long ago, a Yankees manager might have said, "It's not what you want," about the top pitching prospect's first outing of the spring.

Still, Sheffield said, he had his eyes on the regular season and making his big-league debut -- and not on the fact that he didn't last his planned two innings in Sunday's 8-3 win over the Phillies at Spectrum Field before an announced crowd of 7,951.

"I want to show them that I can pitch at this level," Sheffield said. "I know that I can. It's just a matter of me producing and showing these guys."

A two-run home run by Phillies slugger Maikel Franco ended Sheffield's afternoon with two outs in the fourth inning.

Franco blasted Sheffield's belt-high 93-mph fastball, which landed well over the wall in left-center field, caroming off the bottom of bullpen's cement wall.

Immediately, Sheffield was taken out of the game. He lasted 1 2/3 innings, surrendering three runs, all earned, a walk, a hit, a hit by pitch and two strikeouts. He was much better in his first inning, when he struck out Tommy Joseph and Dylan Cozeris swinging in consecutive at-bats before getting a groundout to end the inning.

Sheffield, the Yankees' No. 3 overall prospect and No. 41 in the game, according to Baseball America, hopes to crack the big leagues early in the season and the team's emergency sixth starter. The rest of the rotation seems set.

Sheffield could start the season at Double-A Trenton or Triple-A Scranton/Wilkes-Barre. Last year, he went 7-6 with a 3.18 ERA in 17 starts at Double-A. An oblique injury forced him to miss most of the second half. Then he impressed in the Arizona Fall League, going 2-2 with a 3.10 ERA in five starts.

Manager Aaron Boone mostly liked what he saw.

"It was really important to me that he walks out of there with a lot of positives because, I think, the way I put it, if you had never seen him pitch before and you saw that first inning, he'd open your eyes," Boone said. "It was special. I think he gets going a little bit too fast at times there."

Said Sheffield, "I saw some positives out there (Sunday), but I also saw some things that I need to continue to work on. Just get back at it and get ready for the next outing."

Sheffield, who was in big-league camp last spring, too, said he thought he was "rushing" in the second inning.

"Not catching my breath," he said. "Just rushing a little bit and my arm was dragging."

He said he understood when Boone pulled him and that, overall, the outing "felt good."

"It was good to get out there early in the game while these big-league hitters are still out there. Kind of a test to see where I need to be and what I need to keep working on," he said.

Brendan Kuty may be reached at bkuty@njadvancemedia.com. Follow him on Twitter @BrendanKutyNJ. Find NJ.com Yankees on Facebook.