Pulisic sustained the injury during the USMNT's 2-1 victory over Australia on Wednesday. Jason Connolly / AFP/Getty Images
Christian Pulisic has been diagnosed with a "low-grade injury" to his right hamstring and will miss Milan's Serie A game with Fiorentina on Sunday.
The 27-year-old sustained the injury during the USMNT's 2-1 victory over Australia on Wednesday.
The forward underwent an MRI scan on Friday upon his return to his club which diagnosed the injury.
Milan say he will be re-evaluated again in approximately 10 days.
Pulisic exited Wednesday's friendly midway through the first half after a challenge from Australia defender Jason Geria.
Although he'd felt some ankle soreness last week and played only 18 minutes last week against Ecuador, the treatment he received on the field did not seem to suggest an ankle injury. National team head coach Mauricio Pochettino later confirmed that it was a hamstring issue.
Pulisic is the Serie A joint-top scorer with his four goals, tying him with Bologna's Riccardo Orsolini.
After Sunday's game against Fiorentina, Milan, who are third in the Serie A table and two points off league leaders Napoli, will conclude October by facing Pisa on October 24 and Atalanta on October 28.