Christian Pulisic could be out for nearly a month after he suffered a hamstring injury during Tuesday’s U.S. Men’s National Team friendly win over Australia. 

Italian newspaper La Repubblica reported the news, adding that Pulisic’s club team, AC Milan, is frustrated over the unnecessary risk USMNT head coach Mauricio Pochettino took by starting the American star, despite signs of an ankle issue in recent weeks. 

ESPN reported Pulisic was still in the United States because of a delay on his flight back to Milan and that he still had to be fully evaluated by the Serie A club. 

Tests on Pulisic have been pushed back until Friday, according to the Italian outlet. 

Pulisic is not expected to appear in Sunday’s AC Milan match against Fiorentina, and if the diagnosis is confirmed, he would miss matches against Pisa, Atalanta, Roma and Parma. 

Pulisic had been dealing with a right ankle issue last week and wasn’t put into Friday’s friendly against Ecuador until the 73rd minute as a sub. 

He started Tuesday’s 2-1 win over Australia, but was injured in the 26th minute and had to be subbed out. 

Pochettino alluded to the change in climate — going from Texas to Colorado — as a reason for what led to the injury. 

“I think it’s a thing that is a massive risk. I don’t want to say that Christian or if it’s something because, but I think it was really tough for the player,” Pochettino told reporters. “We know to prepare the game and then to play. We got really sad about this [Pulisic] situation because I think it is difficult.

“I think the [temperature] difference [between Austin and Colorado] and that can affect your body and everything. That is difficult. But yes, that is a thing that we need to fix for the future when we come from Europe because [the altitude] can affect [things].”

Pulisic was AC Milan’s best player this season, putting up six goals and two assists through the club’s first seven matches.