Beltran said he iced his knee during the 45-minute rain delay at the end of the fifth, but his knee stiffened up on him and he was unable to return.
The Mets' doctors were not on hand Friday, but Beltran said trainer Ray Ramirez had him ice the knee and gave him anti-inflammatory medication. Beltran said he would ice the knee every hour Friday night and see how it felt on Saturday.
"The ice made me feel real, real good," Beltran said. "I'm not going to be 100 percent, but if I can tolerate it and play, of course I'll be out there on Saturday."
Beltran said he had been feeling some tendinitis in his knee before Friday.
"I was able to play through it," Beltran said. "It wasn't bothering me like today. Today I couldn't play."
Beltran said he experienced knee discomfort in his left knee about this time the past two years, but not his right.
"Every year, I always feel it by this time, but this year I feel it in the right," Beltran said. "It's kind of sore and swelling a little bit."
Mets manager Willie Randolph said they would consider Beltran day-to-day.
Beltran was 1-for-3 with a run scored and an RBI before he left the game.
Beltran said the injury was unrelated to his stumble in the ninth inning of the All-Star Game on Tuesday. He said it was his foot, not his knee, that hurt him when he was running to first base in that game.
Ryan Crawford is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.