The Mets' Lucas Duda hits a fifth-inning home run against...

The Mets' Lucas Duda hits a fifth-inning home run against the Atlanta Braves at Citi Field on May 4, 2016. Credit: Jim McIsaac

WASHINGTON — The Mets absorbed a major blow on Monday when slugging first baseman Lucas Duda landed on the disabled list with a stress fracture in his back.

Manager Terry Collins said Duda could be out at least six weeks and hinted at the possibility of the absence lingering even longer. David Wright missed nine weeks with the same injury in 2011.

“We’re looking at a fairly long period before he’s gonna be able to get back and do some baseball stuff,” Collins said before Monday night’s series opener against the Nationals. “He’s a huge piece of our team. This guy is a legitimate big bat in the middle of our lineup, so somebody’s got to step up and pick up some of that load. We don’t have a kind of a guy that’s gonna hit 25 to 30 [home runs], but we’ve got to space it out amongst everybody else.”

Duda, 30, was hitting .231 with seven homers and 19 RBIs, but the notoriously streaky slugger has carried the Mets at various points. He hit 57 homers in the previous two seasons, when he established himself as a key threat in the middle of the lineup.

“The first step is to be pain-free,” assistant general manager John Ricco said. “The bone has to heal, and the doctors don’t have an exact time frame for when that would happen. So it is weeks, and kind of a guess right now as to how long that will take. It varies from person to person, but you can’t give it a time frame.”

Wilmer Flores appears to be in line for the bulk of the playing time at first base once he returns from the disabled list, perhaps as soon as Friday. He is expected to play first base when he begins his rehab assignment at Double-A Binghamton on Tuesday.

“Right now because Wilmer’s not very far away, we’re hoping that he gets back,” Collins said. “So we’re just trying to fill in for the next few days to see where Wilmer’s gonna be by the end of the week.”

Until Flores returns, Eric Campbell will see action at first along with switch-hitting utilityman Ty Kelly, who was promoted from Triple-A Las Vegas on Monday.

The Mets also could explore other long-term options, which might include moving leftfielder Michael Conforto to first base despite his lack of experience there. He soon could begin taking grounders at first.

“I’m here to help the team,” said Conforto, whose success at the plate has come with some struggles in leftfield. “So if that’s a spot that they need me to go out there and take ground balls, work on some things, I’m going to do that. I’ll give it my best.”

Mets captain David Wright expressed a willingness to begin taking grounders at first base if needed, though he has no experience at the position. Wright’s balky back might not be able to endure the physical toll of learning a new position. Of course, a move across the diamond could be an eventuality for Wright, who has displayed diminished arm strength.

According to Collins, the Mets are not considering a promotion for highly touted prospect Dominic Smith, who began the season at Double-A. The Mets also discussed but ultimately passed on promoting second-base prospect Dilson Herrera and shifting second baseman Neil Walker to first, where he has never played.

Outfielder Alejandro De Aza has taken grounders at first but appears to be nothing more than an emergency option. The same goes for catchers Kevin Plawecki and Travis d’Arnaud, who remains on the DL with a shoulder injury.

SUBSCRIBE

Unlimited Digital AccessOnly 25¢for 6 months

ACT NOWSALE ENDS SOON | CANCEL ANYTIME