Cuddyer, 36, has been dealing with a bone bruise in his left knee for three weeks. He has not played since last Tuesday, and has started just six of 19 games in July.
Conforto, 22, was selected by the Mets in the first round of the 2014 draft and is the Mets' No. 3 prospect according to MLB.com. He is hitting .312 with five home runs in 45 games since his promotion to Double A this season.
Mets general manager Sandy Alderson was hesitant to call up Conforto too soon, citing examples of young players who don't perform well in the big leagues over short periods of time.
Cuddyer is hitting .250 with 73 strikeouts in 82 games this season. New York's offense currently ranks last in the majors with a .233 team batting average.
The Mets have been battling the Nationals for first place all season, and currently stand 3.0 games back after losing two of three games in Washington this week.
- Erin Flynn