"We needed a pitcher to try to keep everybody healthy down there," manager Buck Showalter said. "And Dom was the option we ended up with."
Smith batted .316 during a breakout season in 2020, but the former first-round pick has struggled to replicate that success. He is hitting .186 this season without a home run in 101 plate appearances, with a .543 OPS.
He has played parts of six seasons in the majors and hasn't played regularly at Triple-A since 2018.
Showalter said Smith will primarily play first base with Syracuse.
"Give him a chance to get back to the things we know he's capable of," Showalter said. "Hopefully, he can do that, and I have a lot of confidence he will and get back up here and help us."
Sending down Smith allows the Mets to keep outfielder Nick Plummer on the roster. Plummer, a 25-year-old former first-round pick with five big league games, had four RBIs in a 13-5 win over Washington on Monday and hit a tying homer in the ninth inning of a 5-4, 10-inning win over the Philadelphia Phillies on Sunday for his first major league hit.
Plummer is a better outfield defender than Smith, making him a useful late-game option for Showalter.
Center fielder Brandon Nimmo was out of the lineup for the fourth straight day with a sore right wrist, but Showalter said he is improving and could start Wednesday or Thursday.
Right-hander Tylor Megill threw a simulated game Tuesday and could make a minor league rehab start soon. Megill hasn't pitched since May 11 with right biceps inflammation.