Conforto was hurt Sunday, sat out two games and then returned in Wednesday's loss to Tampa Bay. Manager Luis Rojas said Conforto aggravated the injury running to first base in the eighth inning.
"He's in the position where he's not going to be able to go out there," Rojas said. "He'd probably aggravate it even more."
Conforto was hitting a career-high .322 with nine home runs and 31 RBIs. He also was sixth in the National League in on-base percentage (.412), tied for eighth in runs (40) and ninth in batting average.
"He had a great regular season," Rojas said. "He was solid throughout, from the beginning until he was not able now. He just played really well. Offensively, his numbers are there. He was unbelievable. He did a great job improving some of the parts he said he wanted to improve in his game offensively, and he also improved some of the parts he wanted to improve defensively."