Amed Rosario headed a list of five prospects the Mets protected from the Rule 5 draft. The others include righthanders Chris Flexen and Marcos Molina, outfielder Wuilmer Becerra, and catcher Tomas Nido.

All were added to the 40-man roster by Friday’s deadline, making them ineligible to be chosen in the Rule 5 draft on Dec. 8. The moves brought the Mets’ 40-man roster to capacity, meaning the Mets would need to clear space in event of any other additions through free agency.

Rosario, who turns 21 on Sunday, is regarded as one of baseball’s top prospects. The Mets previously have deemed the shortstop to be virtually untouchable in trade talks, viewing him as a potential future star.

Named the Mets’ organizational co-player of the year, he hit .324 with five homers and 71 RBIs in 120 games between Class-A St. Lucie and Double-A Binghamton. He also played in the annual All-Star Futures Game.

Flexen, 22, was a 14th-rounder in the 2012 draft. In 25 starts with Class-A St. Lucie, he went 10-9 with a 3.56 ERA.

Molina, 21, posted a 3.78 ERA in seven games during the recently concluded Arizona Fall League. He missed the regular season recovering from Tommy John surgery.

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Becerra, 22, had his season at Class-A St. Lucie cut short by surgery to repair the capsule in his right shoulder. But first, he hit .312 and was named a Florida State League midseason all-star.

Nido, 22, hit .320 for Class-A on the way to the Florida State League batting title. He was also named one of the league’s midseason and postseason all-stars.