The Mets optioned Vientos to Triple-A Syracuse on Tuesday, Mike Puma of the New York Post reports.
Vientos contributed a walk-off home run in Sunday's extra-innings win over the Cardinals but now finds himself back in the minors as Starling Marte returns to the active roster. With J.D. Martinez with the club and Brett Baty absorbing most of the at-bats at third base, there's no path to regular playing time for Vientos right now.