It is a major blow for Duda, who led the Mets with 57 home runs from 2014-15, batting .249 with an .834 OPS and 165 RBIs over that two-season stretch. Even if Duda were able to return immediately at the end of his rest period, there would be less than a month remaining in the regular season for him to ramp up baseball activities, complete a rehab assignment and return to the Mets.
"Maybe if we reach the third round of the playoffs," Alderson said. "I don't know. It doesn't look good."
In Duda's absence, the Mets will continue to use James Loney most days at first base. Acquired from the Padres shortly after Duda's initial diagnosis in May, Loney was batting .284 with six home runs in 54 games entering Wednesday. His production has allowed the Mets to move on from Duda relatively seamlessly, despite Loney's relative lack of power.
"He's been great," Alderson said. "He's done a very nice job for us."
With Loney due to become a free agent after the season, the Mets could look to convert an outfielder such as Michael Conforto or Jay Bruce to first base at that time. But considering Loney, Kelly Johnson and Wilmer Flores are all capable of playing first base, the Mets aren't likely to do so this season -- "You can't just flip somebody to a position like that overnight," Alderson said. Flores in particular could draw increased playing time at first once Asdrubal Cabrera and Jose Reyes come off the disabled list, limiting the need for Flores on the left side of the infield.
Where all of this leaves Duda next year remains to be seen. Arbitration-eligible for the third time this season, Duda is making $6.725 million, and will be due for another raise this winter before becoming eligible for free agency after the 2017 season. Missing most of this season makes Duda a non-tender candidate, though the Mets have not yet discussed that even internally.
"It's always a concern when a player's not able to come back late in the season, and demonstrate he's healthy going into the following season," Alderson said. "But I don't concern myself with that now. I've got other things to deal with. And we'll know a little more in the next 30 to 45 days."
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.