PORT ST. LUCIE, Fla. — On the first pitch he’s ever seen from an opposing pitcher as a professional, Mets outfield prospect Tim Tebow cracked an opposite field home run Wednesday.

Tebow hit a 91-mph fastball up in the strike zone from 6-5 lefthander John Kilichowski, a 22-year-old former Vanderbilt standout who was the St. Louis Cardinals’ 11th-round pick in the June draft.

In the intrasquad games Monday and Tuesday, the lefty-swinging Tebow had only faced righthanders.

“I just tried to be aggressive,” he said. “Sometimes because it’s a lefty, if you’re able to stay in there you can see it a little easier sometimes.

“I just tried to stay back and have good rhythm, something we’ve been working on, and just tried to barrel it up.”

The last home run Tebow hit in competition was in 2005 as a junior at Nease High School in Ponte Vedra Beach, Florida, playing in a state semifinal game.

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Tebow said he didn’t see the home run go over the fence in left-center field. “I put my head down; I was running,” he said.

When he returned to the dugout, the 29-year-old Tebow was mobbed by the other Mets players, most of whom are ages 18 and 21.

“It was fun. I’ve got a really good relationship with the other guys,” Tebow said. “We’ve had a chance to hang out the last couple of nights. We saw a movie last night and dinner the night before. I think we get along really well and root for each other, so it was fun.”

Mets manager Terry Collins saw a film clip of the home run and “thought it was pretty cool what the players did. So, the story continues. Again, we all sit there and say . . . a majority of people think, OK, he’s too old, he can’t do it, he hasn’t got enough time . . . He’s such a winner, he’s such an overachiever, that he just may do something people said can’t be done.”

Of the 58 players in the Mets’ Instructional League camp, the only three other than Tebow who are over age 22 are pitchers returning from arm surgeries.

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To give Tebow extra at-bats, the Mets had him bat once in each of the first six innings. He did not have any more hits, but he put the ball in play every time and had solid contact a few times.

On his fourth at-bat, and the third time he faced 22-year-old Cardinals righthander Ramon Santos, who pitched this season in the Rookie-level Appalachian League, Tebow hit a deep line drive, but centerfielder Vince Jackson ran it down.

“I liked a lot of my at-bats today,” Tebow said. I felt like I hit the ball really hard four of the six times.”

On two of his at-bats — one of which he squirted toward the third baseman and another ground out to the shortstop — he said he thought he swung late.

“Four of the at-bats I felt really, really good about,” he said. “I didn’t swing at any breaking balls. I didn’t feel like I got fooled on seeing it, felt good seeing it out of the hand. I was just late on a couple of the fastballs.”

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Baseball, Tebow said, “is a different type of work” from football.

“Not everything is grit your teeth and flex, and go will it to be done as much,” he said. “Sometimes you can do that in football, though not always at the quarterback position, but sometimes you can still do it.

“This [baseball] is something where maybe if you’re fatigued and you’ve worked enough for the day, you’ve got to wait and do more tomorrow, because working when you’re fatigued you can create bad habits.”

With Marc Carig in Miami