Bay joined the Mets' Triple-A affiliate in Buffalo on Saturday as part of his rehab assignment after going 0 for 6 with two walks in two games with Class A St. Lucie. The Florida State League activity marked Bay's first game action since he suffered a concussion June 15.
Outfielder Mike Baxter is also nearing a return from the disabled list.
Baxter suffered a displaced right collarbone making a no-hitter-saving catch for Johan Santana in left field on June 1. He is due to begin a rehab assignment Sunday with St. Lucie, according to Collins.
The news of impending returns came as right fielder Lucas Duda was out of Saturday's lineup with tightness in his left hamstring.
The hamstring has been an issue for about a week and Duda hoped it would heal during the All-Star break. However, Duda continued to feel tightness during Friday's second-half opener against the Atlanta Braves and Collins plans to hold him out of the starting lineup through the weekend.
"It's been bothering him for a while, and he thought the rest was going to help him," Collins said. "And it's stiffened up on him a little bit. We're going to give him a couple of days' rest, use him late in the game if we need him. But, as I told him again today, I'd rather have him on the bench than have him start the game -- especially in this humidity -- and have it cramp up and have to pull him out in the third, because then it really shortens the moves you can make."
Duda said he wasn't a big deal and expects to be able to pinch hit if necessary.
The Mets also have decisions to make with respect to starting pitching now that right-hander Dillon Gee likely is lost for the season following surgery Friday in St. Louis to repair a damaged artery in his pitching shoulder.
The Mets plan to use a four-man rotation until next weekend, with Chris Young coming back on standard rest Wednesday against Washington after throwing only 71 pitches in an ineffective outing Friday at Turner Field.
Harvey is due to start Monday for Triple-A Buffalo, and Collins said a bevy of Mets officials will watch that start to gauge Harvey's major-league readiness. Batista walked four and allowed a hit while recording only four outs in relief of Young on Friday night against the Braves.
Collins said right-hander Zack Wheeler is not a consideration for a spot in the rotation at this point, but the prized prospect will be strongly considered next month for a major league promotion.
Wheeler, who was obtained from the San Francisco Giants in the trade for Carlos Beltran last year, currently is pitching for Double-A Binghamton, and general manager Sandy Alderson has forecast a promotion soon to Buffalo.