The group with the most continuity for the 2021 Mets is their outfield. Dominic Smith, Brandon Nimmo, and Michael Conforto—the left, center, and right fielders respectively—have been Mets mainstays since 2019, when Smith had his breakout campaign, and Nimmo debuting in 2016 and Conforto in 2015. This trio is most likely to make the bulk of the starts for the 2021 group, with guys like Kevin Pillar and Albert Almora pitching in defensively and against tough lefties.
The outfield is also arguably the most interesting group, mostly because how the lack of a designated hitter has virtually handcuffed the Mets into playing a defensively sub-optimal group, with the hope that their offensive contributions will outweigh that the group will almost certainly give to a potent Mets lineup.