Castro, activated off the disabled list July 15, reinjured his hamstring while running out a ground ball on Wednesday at Minnesota. He played in the first two games of the series at Seattle on Thursday and Friday, with one hit in eight at-bats.
"We're not sure it's the exact same spot," Girardi said. "He'll probably go on the DL starting tomorrow. It's frustrating. He's frustrated. He had an MRI this morning, and we've got to put him down for a bit."
Castro is hitting .307 with 12 homers and 45 RBIs in 79 games. He said the MRI was scheduled after noticing discoloration.
"It's frustrating because my job is to come here and play hard every day," he said. "It's kind of in my head right now.''
Castro missed seven games last September after straining his right hamstring.
"I had hamstring problems in Chicago, but it was back in spring training," said Castro, who was traded from the Cubs to New York following the 2015 season. "The first time it happened in the season was last year."
Girardi said Tyler Wade will be recalled from Scranton/Wilkes-Barre, where the infielder is hitting .313 with six homers and 30 RBIs. Wade was optioned to Triple-A on July 15 after a nine-game stint with the Yankees, when Castro was previously injured.