Flores, who backs up Duda at first and also plays everywhere else on the infield, has an infection in his knee and could also face an extended absence. Doctors gave Flores new medication Thursday, and the Mets will wait to see how Flores responds to it.
With Duda and Flores both out, Jay Bruce started at first base for the first time since 2014. Bruce played the position three times for the Reds that season, and also saw time at first base for the Mets this spring.
"If Lucas is unavailable for an extended period, I don't know what our next move would be," manager Terry Collins said.
Dominic Smith, the first baseman at Triple-A Las Vegas and the Mets' No. 2 prospect, didn't have a great Spring Training but is off to a fast start with the 51s. Smith entered play Thursday with a .364 batting average and two home runs in 14 games.
If the Mets put Duda and/or Flores on the disabled list, they could also recall infielder T.J. Rivera from Las Vegas. Rivera was optioned to Triple-A on Friday, so he can't come back before Monday unless it is to replace an injured player.
Danny Knobler is a contributor to MLB.com based in New York. This story was not subject to the approval of Major League Baseball or its clubs.