"I'm real concerned, there's no question," Collins said after the Mets' 3-1 win over the Brewers. "I'm really concerned that this is going to keep this guy out for a while. But that's just me. I'm not the doctor."
Duda, who leads the Mets with 64 homers since the start of the 2014 season, first sat out Tuesday with what the Mets called stiffness in his lower back. The first baseman returned to play Thursday and Friday, going 1-for-7 in those games, then was a late scratch from Saturday's lineup. He underwent an MRI that morning, before returning to Manhattan for additional testing on Sunday.
Duda declined comment upon arriving at Citi Field from the hospital Sunday, and was unavailable to speak following the game.
Overall this season, Duda is hitting .231 with seven home runs, but just .171 with no homers over his last 13 games. In the short term, Eric Campbell will start in Duda's place at first base. Wilmer Flores, the team's primary first-base sub heading into this season, is due to begin a rehab assignment Tuesday. He could rejoin the Mets as soon as Friday, when he is first eligible.
Anthony DiComo has covered the Mets for MLB.com since 2008. Follow him on Twitter @AnthonyDiComo and Facebook, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.