Valdez was removed from Friday's contest against the Cubs with left hamstring discomfort, Aiden Stepansky of MLB.com reports.
Valdez grounded out to shortstop in the top of the sixth inning and almost immediately came up limping after exiting the batter's box. The Pirates could have more information on his status after the game, but it's an injury that could end the rookie's season. Valdez was 0-for-3 with a pair of strikeouts in the game before exiting.