"They said it was mild, and usually I'm a quick healer, so hopefully that's the case," Nieves said.
Nieves said he hopes to avoid a stint on the 15-day disabled list. The Phillies will know more on Thursday in St. Louis.
"Feeling the hamstring cramping, I think it's just hydration," Nieves said. "I'll drink some water and get a couple of anti-inflammatories, and hopefully it'll be fine."
Nieves is hitting .259 with five doubles, one home run and four RBIs in 14 games, with Carlos Ruiz on pace to start a career-high 130 games. Ruiz, 35, has never started more than 113 games behind the plate, having spent each of the previous five seasons on the disabled list.
If Nieves is placed on the DL, Cameron Rupp and Tommy Joseph are the only other catchers on the Phillies' 40-man roster. Rupp is likely to be promoted in that case; he impressed in four games late last season, but he is hitting just .154 with a .635 OPS in 125 plate appearances with Triple-A Lehigh Valley.
Joseph has missed much of the last two seasons because of injuries. He has not played since May 9 because of a left wrist injury.