Despite being older than Davis, Lucas Duda has not been an everyday starter for a full major league season yet.
Duda made his major league debut in September of 2010 as a late season call-up. In 2011, Duda got some playing time at first base after Davis' injury and split time in right field as well. He hit .292 with 10 home runs and 50 RBI that season.
A year later, Duda hit .239 with 15 home runs and 57 RBI and was the Mets' starting right fielder until getting demoted in late July for about a month. After being brought back up, Duda played in left field and filled in occasionally at first base.
In 2013, Duda began the season as the regular left fielder, but a rib injury sidelined him for a while and the arrival of Eric Young Jr. pretty much ended his time as a left fielder. After being activated from the disabled list, Duda was in the minor leagues for a few weeks before getting recalled back up to the Mets. Ironically, shortly after his return, Davis suffered a season-ending oblique injury, which led to Duda being the regular first baseman for the remainder of the season.
All in all, Duda simply has not had a full season to really prove himself at the major league level. The power potential is there, but 15 home runs per season will not be enough to satisfy all the Mets fans. A player with Duda's size and power potential should be able to hit 25-30 home runs per season. If the Mets were to give Duda an everyday opportunity at first base, he may be able to really prove himself. But until then, Duda will not have too much going for him in regard to proven success.