The Mets activated Vientos (hamstring) from the 10-day injured list Friday.
Vientos is in the lineup for Friday's series opener in Pittsburgh, batting sixth against Pirates right-hander Mitch Keller. Vientos has been sidelined since June 2 and is slashing an underwhelming .230/.298/.380 with six home runs, 21 RBI and 22 runs scored across 208 plate appearances this season.