Bay has been on the disabled list since fracturing a rib on April 23.
The Mets left fielder was the designated hitter in his first two rehab games, but was scheduled to play the field on Monday night against the Tampa Yankees. Bay is a combined 2-for-6 with one RBI during the assignment.
Upon Bay's return, Collins will be forced to juggle time between five outfielders. In addition to Kirk Nieuwenhuis, Andres Torres and Lucas Duda, the skipper said he will try to incorporate Scott Hairston into the lineup, specifically against left-handed pitchers. Hairston boasts a .339 average against southpaws this season, and has hit five of his six home runs against lefties.
Following the three-game set with Washington, the Mets travel across town to Yankee Stadium for a weekend series, followed by a three-game road set against the Tampa Bay Rays.
Collins was grateful for the six consecutive games his team will play in American League parks.
"We've got six games with a DH," Collins said. "We're lucky we can maneuver that outfield and get everybody in there."