Two years ago, Mets outfielder Michael Conforto finished his first professional season in the minor leagues in early September. He went home for a week or so and then reported to Port St. Lucie, Florida, for a unique baseball institution called Instructional League.

Or, as it’s known throughout the game: instructs.

Instructs are a three-week boot camp of baseball. The brightest and youngest prospects, many of them teenagers, report to an organization’s spring training facility in Florida or Arizona for individualized drills in the morning and games in the afternoon.

In this case, the games are not the thing. The play’s the thing.

The games are not televised. There are no boxscores in the morning paper. No admission is charged because usually there is no one to charge admission to.

“I don’t think there were any fans, honestly,” Conforto said of his only Instructional League experience in 2014.

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That will not be the case for the Mets for this year’s Instructional League, which begins on Monday on the back lots of the Tradition Field complex.

Oh, the team still will not be charging admission (or a parking fee). But there will be fans — because along with 57 actual prospects, former NFL quarterback Tim Tebow will be on hand to begin his baseball career after signing a minor-league contract with the Mets on Sept. 8.

Tebow, a would-be lefthanded-hitting outfielder, is 29 years old. He has not played baseball since 2005, when he was a junior in high school. The former Heisman Trophy winner and two-time national champion at Florida flopped in the NFL, with his last regular-season game coming with the Jets in 2012.

Starting on Monday, Tebow will be taking to the diamond with prospects as young as 17 (outfielder Raul Beracierta and infielder Gregory Guerrero) and as old as 25 (pitcher Cameron Griffin).

Also on this year’s roster the Mets released on Friday are a pair of Long Island pitchers, righthander Justin Dunn and lefthander Anthony Kay, who were the team’s first two picks in the June draft.

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If Conforto hadn’t developed as quickly as he did, he might have been back in Instructional League after the 2015 season. Many players go more than once.

“I think I was supposed to,” Conforto said. “But I ended up playing in the World Series. I’ll take that every time.”

The Yankees, who also will open their Instructional League on Monday in Tampa, scouted Tebow along with all but two of the 30 big-league teams at his showcase workout in Los Angeles last month.

The Yankees are not believed to have made an offer to Tebow. But they also will have a designated Instructional League celebrity: the sort-of-retired Alex Rodriguez, who is expected to show up at some point unannounced to serve as an instructor.

It’s part of the new role he agreed to with Hal Steinbrenner when A-Rod’s Yankees playing career ended with great fanfare last month.

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“We expect him to be there,” a Yankees spokesman said on Friday. But the Yankees are not planning to announce beforehand which day A-Rod will arrive to work with top infield prospects such as Gleyber Torres and Jorge Mateo.

Rodriguez probably will announce it himself on Twitter.

The Mets have taken great pains to deny that they signed Tebow either to generate publicity or make marketing money off his prodigious fame. General manager Sandy Alderson said it was “strictly driven by baseball.”

The baseball will begin for Tebow in the same place and same way it began nine years ago for a 16-year-old Mets prospect from Venezuela named Wilmer Flores.

Flores, now a Flushing folk hero, reported to Instructional League in 2007 for his first experience as a professional baseball player. He had signed in August and did not play in the minor leagues before showing up in Port St. Lucie.

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“It was my first time for everything and everything was just weird,” Flores said. “Going out there every day early. A lot of ground balls. The days were just longer. Instructional League’s all about young players. I was 16, but some other guys were 17, 18. It’s like the military. All of the guys doing the same things. A lot of meetings, a lot of talking.”

For Yankees utilityman Rob Refsnyder, Instructional League was his first exposure to a new position, second base, after he played the outfield at the University of Arizona and in his first minor-league season.

Refsnyder went to the Instructional League in September 2012 and took oodles of early-morning ground balls from minor-league coach Carlos Mendoza.

“He hit me hundreds and thousands of ground balls for two years,” Refsnyder said. “My second year, they didn’t even let me hit. Just game after game and reps at second base. Instructs are the best. It’s hard work. It’s hot. It’s miserable. But they can change your career.

“You hear a lot of younger guys complain about them: ‘I don’t want to go to instructs. I just want to go home.’ You’re away from your girlfriend, your family for a couple weeks. ‘I don’t want to do this.’ And then you get there and you realize what it’s all about. What other situation could you have 12 coaches of the highest caliber investing their whole day and just trying to get you better for a couple weeks? I couldn’t have gotten to the point last year of making my [major league] debut without instructs.”

Unlike A-Rod or some of the big-name “guest instructors” who show up in spring training, Instructional League coaches generally are a team’s minor-league managers, coaches and staffers — the grunts who are hoping to hone their skills and make it to the bigs someday, too.

Mets infielder Jose Reyes credits a coach named Rich Miller, who helped him with bunting and base-stealing in Instructional League in the early 2000s. Miller, a roving instructor at the time in the Mets’ minor leagues, now is a senior adviser for player development with the Toronto Blue Jays.

“He helped me a lot,” Reyes said. “A lot. When you’re young, you want to play the most you can to try to get better. To go to Instructional League, it gets you better. Not too many people are going to be there. They’re going to have more time to work with you on whatever you need.”

Said Refsnyder: “Tebow will probably have to go through all the basics of everything. He seems like a good person, so I hope he really invests a lot of time in instructs. There’s literally every coordinator, every outstanding coach, and you just play baseball.”

Tebow might never make it to Citi Field. The odds certainly seem against him. Then again, there’s no doubting his athletic ability, though whether that will translate to baseball remains to be seen.

“He needs to work,” Reyes said. “It is a hard game. He’s going to have an opportunity to figure it out, to see if he could do it or not.”

Instructional League will be circus-like for the first two days, as the national media as well as curious fans are expected to descend on Port St. Lucie. Tebow will hold news conferences after his first two workouts.

In another unique twist, Tebow will train with the Mets only four days a week. He will leave on Friday to continue his college football broadcasting career with the SEC Network. Sunday is a day off for everyone during Instructional League.

Some in baseball have scoffed at the whole idea of the Mets signing Tebow, as if some sacred covenant has been broken.

Then there are those such as Flores, whose eyes light up at the mention of Tebow’s quest. Flores understands the impact Tebow’s presence might have on the teenagers he’ll be working out with in Instructional League.

“You walk out of the door and you see Tim Tebow tying his shoes,” Flores said. “I wish I was there to see him. It’ll be interesting to see how it turns out.

“You can never say he’s not going to play in the big leagues. Never. Because I’m sure to a lot of players here, somebody said, ‘You’re not going to play in the big leagues.’ If you have talent, it takes time, but you can never say that he’s not going to play.”