WASHINGTON (CBSNewYork/AP) — New York Mets manager Terry Collins expects first baseman Lucas Duda to be out at least four to six weeks and maybe longer with a stress fracture in his lower back.

The Mets placed Duda on the 15-day disabled list Monday with the back problem that had been bothering him for some time. Collins gave no official timetable on Duda’s absence, but said the 30-year-old won’t be able to do baseball-related activities for some time.

“We’re looking at a fairly long period before he’s going to be able to get back and do some baseball stuff,” Collins said before his team’s game against the Washington Nationals.

“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 going to hit 25 to 30 (home runs), but we’ve got to space it out amongst everybody else.”

Duda is hitting .231 with seven home runs and 19 RBIs after putting up 27 home runs last season and 30 in 2014. Eric Campbell was at first base Monday and will shoulder most of the load for now, Collins said, at least until Wilmer Flores returns from a hamstring injury.

Collins said Flores, who will begin his rehab Tuesday in Binghamton, is the Mets’ best long-term option in Duda’s absence. Ty Kelly, called up from Triple-A Las Vegas, is another option and more plausible than moving third baseman David Wright or outfielders Michael Conforto or Alejandro De Aza to first.

“We’re not in a position right now to just test guys,” Collins said. “Right now in our situation, with the expectations and where we’re sitting, (it’s) pretty dangerous to put a guy, an inexperienced guy, at a position that he’s never been at before.”

Collins said Duda’s injury is the same one Wright suffered in 2011. Wright has been bothered by back problems since.

Wright to first base is something Collins mentioned to the 33-year-old veteran, but it’s not the first choice.

“I mentioned it to David and here’s the answer, which I expected to hear: ‘Whatever the team needs, I’m willing to try it,'” Collins said. “But we’re not ready to go there yet.”

Collins said he didn’t know how Duda got hurt and only mentioned it to team personnel a few days ago. He has missed four of the Mets’ previous six games.

“As you can imagine, he’s really disappointed,” Collins said. “We also know he’s a tremendous worker, and he will put in the work needed so that he can get back.”

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