Right-hander Drew Smith and outfielder Kevin Kaczmarski were called up from Triple-A Las Vegas on Friday before the opener of a three-game series against the Los Angeles Dodgers.
Robles was designated for assignment, removing him from the 40-man roster. New York has seven days to trade, release or send him outright to the minors. The right-hander was 2-2 with a 5.03 ERA in 16 appearances during his fourth season with the Mets. He allowed seven home runs and walked 10 in 19 2/3 innings.
Sewald and fellow right-hander Chris Flexen were optioned to Las Vegas following Thursday's loss at Colorado. Sewald was 0-4 with a 4.85 ERA in 26 games, and Flexen had an 11.57 ERA in 2 1/3 innings.