Mets prospect Matt Harvey throws a live batting session during...

Mets prospect Matt Harvey throws a live batting session during spring training. (Feb. 25, 2012) Credit: Alejandra Villa

VIERA, Fla. -- Mets top prospect Matt Harvey was supposed to throw about 90 pitches Sunday in his first start against major-leaguers.

Instead, he threw 43.

In one inning.

Harvey allowed five runs and seven hits, including three home runs, in a one-inning outing in the Mets' 12-0 loss to the Nationals at Space Coast Stadium.

The seventh overall pick in the 2010 draft, who turns 23 Tuesday, impressed with his high-octane stuff earlier in camp, when he threw four hitless, scoreless innings in two big-league relief appearances.

On Sunday,, Harvey gave up a home run by Ian Desmond on his second pitch. Then back-to-back doubles. Then a monster two-run home run by Jayson Werth. Then, after two outs, a windblown homer by Roger Bernadina and two more singles, including one by pitcher Stephen Strasburg.

Harvey's inning, and outing, ended with a called third strike to Desmond, the 10th batter he faced.

"Just couldn't execute," Harvey said. "I was getting ahead of myself a little bit. Tried to keep the ball down, but the more I tried it, it just didn't happen. I just wasn't able to execute."

Harvey surmised that his body was moving too quickly and his arm didn't catch up. He admitted he was "a little amped up" for the assignment, which came in part because the Mets wanted Dillon Gee to skip the Nationals. Gee already had faced them twice in spring training and will again in the second series of the regular season.

The Mets also didn't mind the opportunity to see how Harvey handled his first time starting against a big-league lineup.

Last season, his first as a professional, Harvey started 14 games in Class A and 12 in Double-A, finishing with a 13-5 record and 3.32 ERA.

Regardless of whether he begins this season in Double-A or Triple-A -- the Mets haven't decided yet -- Harvey could be one of the first pitchers called up if the big club needs a starter. The Mets don't have a lot of depth after their top five.

But that could be getting ahead of things, which is something Harvey did Sunday, to his detriment on the mound.

"Something I learned from today is slowing everything down," he said. "Whether it's getting off the mound and taking a couple extra breaths or . . . It wasn't nerves or anything like that. It was me being a little amped up and my body was moving a little too quick . . . My body felt great, arm felt great. It was just a matter of getting the ball down throwing my pitches, and I wasn't able to do that."

Of Werth's homer, which went over the leftfield stands, Harvey said: "He hit it pretty good. It almost seemed like I told him what was coming and he hit it. He's a professional hitter. He makes a lot of money for it, so if I'm missing my spots and leaving it over the middle, he's going to hit it."

Manager Terry Collins said a mouthful when he said, "He's better than that outing.

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"Obviously, I'm sure he was all jacked up. It's Strasburg and a lot of things. But if he gets something out of it, it means that you just can't rear back and throw. You've got to make pitches. He left a lot of balls up today. So hopefully, next time we see him, it'll be a lot better."

Strasburg went five innings, gave up five hits and a walk and struck out five. The Mets don't think Harvey has Strasburg-type stuff -- few do -- but they think he has a bright future.

"He's closer to the major leagues than what he showed today," Collins said. "It was just a crappy day."