Mets rightfielder Michael Conforto looks on from the dugout before...

Mets rightfielder Michael Conforto looks on from the dugout before an MLB game against the Phillies at Citi Field on Sept. 19. Credit: Kathleen Malone-Van Dyke

CARLSBAD, Calif. — Michael Conforto is closer than ever to leaving the Mets.

He will reject the team’s qualifying offer and head fully into free agency, a source familiar with the process said Monday.

The qualifying offer, issued to Conforto on Saturday, was a one-year, $18.4 million contract. That he declined it so quickly — when the deadline to do so isn’t until Nov. 17 — suggests he has received significant interest in the opening days of free agency, enough that he was comfortable saying no thank you to the certainty of the short-term deal with the only major-league team he has known.

The Mets still are able to re-sign Conforto if the parties choose to reunite, though their level of interest in doing so is unclear. If Conforto signs elsewhere, the Mets will receive a bonus pick in the 2022 draft as compensation.

Last season, his seventh in the majors, Conforto was mediocre — if not downright disappointing, relative to his usual self. He hit .232 with a .344 OBP and .384 slugging percentage.

Despite the down year, Conforto has produced at a level that likely will encourage teams to consider giving him a long-term contract. His .255/.356/.468 career slash line qualifies as well above average. That he is still only 28 and can play both corner outfield spots — and centerfield in a pinch — adds to his attractiveness on the open market.

Should Conforto indeed leave the Mets, they don’t have an obvious in-house replacement. Free-agent rightfielders include Nick Castellanos, Avisail Garcia and World Series MVP Jorge Soler. Highlighting the batch of centerfielders are Starling Marte and utilityman Chris Taylor.

The only other Mets free agent to receive a qualifying offer was Noah Syndergaard, who is much more likely to accept. He said in September he was "hoping for" and "would be extremely grateful for" it.