Beltran, who hit three home runs Thursday, said he woke up Saturday with a puffy, itchy eye and wasn't sure how it happened. He was given drops by Mets trainer Ray Ramirez for what could be conjunctivitis, though the Mets weren't calling that the official diagnosis.
"I just woke up feeling like there was something in my eye," he said. "Maybe I scratched it during the night. It just burns."
Beltran said it improved with treatment but "it still needs to get better in order for me to play."
Beltran was replaced in the lineup by Fernando Martinez, who pinch hit a home run in the Mets' 6-4 win Friday night. Martinez went 1-for-4 in the Mets' 7-3 loss Saturday.
Coincidentally, manager Terry Collins said before the Beltran announcement that he wanted to find at-bats for Martinez, the 22-year-old who was called up Thursday when Ike Davis went on the disabled list.
Martinez used to be a centerfielder, but Collins said he isn't thinking of playing him there even with Angel Pagan out. Martinez has an arthritic knee and the Mets think he is better suited to a corner spot.
Scott Hairston started in center Saturday against lefthander J.A. Happ. Jason Pridie has been playing against righties. Collins said he would not rule out using Jason Bay or even Beltran in center as Pagan (oblique strain) has only just begun baseball activities again.
Collins said putting Beltran back in center would be "unfair." But he added: "I talk to this guy every day. So if that's what we think is the best move, I know one thing: Carlos Beltran will be open to anything he can do to help this club."
Collins stressed that playing Beltran in center would be only a "one-day thing" if it happens.
Pedro Beato (right elbow) reported to Triple-A Buffalo to begin a rehab assignment.