In addition to searching for a manager to replace Terry Collins for next season, the Mets likely will be in the market for a new pitching coach.

According to multiple industry sources, the team is preparing to inform pitching coach Dan Warthen he won’t be retained for 2018, following a season in which the Mets’ pitching staff, besieged by injuries and underperformance, has imploded.

The 64-year-old Warthen is the longest-tenured member of the Mets’ field staff, having assumed pitching coach duties in June 2008, after Rick Peterson was fired, along with manager Willie Randolph.

The Mets, who defeated the Braves 4-3 Tuesday night at Citi Field, entered the game with a 5.02 ERA that ranked next-to-last in the National League. A source indicated team officials simply believe it’s time for a change after a “historically” bad season by the pitchers.

Mets bullpen coach Ricky Bones and the organization’s minor league pitching coordinator, Ron Romanick, are the top candidates to replace Warthen, according to sources. Frank Viola, who has spent the past four seasons as the pitching coach at Triple-A Las Vegas, is unlikely to be considered for the job, according to sources. It is unclear if Viola will remain in the organization.

External candidates could include Red Sox director of pitcher development Brian Bannister, who broke into the majors in 2006 with the Mets, and former Oakland pitching coach Curt Young, who has ties to general manager Sandy Alderson from the Athletics.

Noah Syndergaard, Matt Harvey, Zack Wheeler, Steven Matz and Seth Lugo were among the pitchers the Mets lost to injuries for extended periods this season, but the team also saw a regression from several members of that crew, in addition to Robert Gsellman’s maddening inconsistencies.

The bullpen was also in ruins, with Jeurys Familia absent for three months after undergoing surgery to remove a blood clot from his right shoulder. But the Mets received disappointing results from, most notably, Fernando Salas and Hansel Robles. The bullpen further was exposed following the July 31 trade that sent Addison Reed to the Red Sox.

Barring a last-minute change of heart by co-owner Fred Wilpon — something club sources say is unlikely — the 68-year-old Collins will be informed as soon as Monday that his contract will not be renewed.

As The Post reported this week, potential candidates for Collins’ position include Robin Ventura, Alex Cora, Kevin Long, Bob Geren and Chip Hale, all of whom have ties to the Mets.

Long, the team’s hitting coach, has an expiring contract and could leave the organization if he is not elevated to manager. Team officials are intrigued by the 50-year-old Long, based on his communication skills, relationship with the players and his thorough understanding of analytics.

If Long were hired as manager, assistant hitting coach Pat Roessler likely would be promoted to fill Long’s position.

And if Bones is promoted to pitching coach, the Mets would need a new bullpen coach. Bones has held the position for the past six seasons.

Under Warthen’s guidance, the Mets developed pitchers such as Harvey, Syndergaard, Matz and Jacob deGrom. But all have spent time on the disabled list the past two seasons, leaving the organization scrambling to fill the rotation.

Warthen, who had previous stints as the pitching coach with the Padres and Tigers, has hinted in recent weeks that he may retire.