𝓤𝓷𝓲𝓽𝓮𝓭 𝓝𝓮𝔀𝓼

Tuesday was a good night for the U.S men’s national team, but less so for Christian Pulisic.

The 2-1 friendly victory over Australia might have been encouraging enough for Mauricio Pochettino but the loss of Pulisic to injury midway through the first half cast a shadow over the latest step towards the 2026 World Cup finals.

The full extent of a hamstring problem will not be known until Pulisic is examined in Milan, but the schedule of the USMNT during this international break was cited by Pochettino as a contributory factor.

The Athletic looks at why the Argentine made his comments and whether he was justified in doing so.

What happened to Pulisic?

It was a short night in Commerce City for the USMNT’s star forward.

After being on the end of some forceful tackling through the opening stages of Australia’s visit, Pulisic was unable to continue once he was clipped from behind by defender Jason Geria in the 26th minute.

Lengthy treatment followed before the decision was made to withdraw Pulisic, who appeared visibly upset when later sat on the bench. It was later confirmed to be a hamstring injury.

Christian Pulisic walks off after his injury on Tuesday (Jason Connolly/AFP via Getty Images)

What did Pochettino say about it?

Pochettino questioned the logic of playing Australia in Colorado four days after 1-1 draw with Ecuador in Austin, Texas.

As well as losing Pulisic during the game, Malik Tillman had also been unable to feature due to “feeling something” in his hamstring.

Pochettino did not attribute either injury directly to the scheduling but said it was a “massive risk” to subject players to a significant change in climate during this break.

“It’s not a criticism, but when you have days in training in Austin where it’s (85-95 degrees Fahrenheit; 29-35 degrees Celsius) then you come to Denver with the altitude and it’s really, really cold — it’s a massive risk,” said Pochettino.

“I don’t want to say this is why Christian or Malik felt something, but it’s tough on the players. We’re really sad about this situation because it’s difficult. It’s something we need to fix in the future.”

What do experts say about the risks of going from one temperature extreme to another?

This is a factor long considered to offer a heightened risk of injury.

“When footballers move quickly from a warm climate to a cold one, the main concern isn’t just discomfort — it’s a high risk of non-contact soft tissue injuries,” says Geoff Scott, formerly head of medicine and sports science at Premier League club Tottenham Hotspur, where he worked with Pochettino between 2014 and 2019, and who subsequently set up recovery and performance brand Hauora.

“We’re talking about muscle pulls and tears. The problem starts with the muscle itself. Cold air causes the body to trigger vasoconstriction, which narrows the blood vessels near the skin and reduces blood flow to the muscles. This drop in temperature makes the tissue’s essential properties change.

”A cold muscle loses its natural elasticity and stretch. It becomes stiffer and less able to handle stress. When a player then bursts into a full-speed sprint or executes a sudden, sharp turn, that rigid, cold tissue can’t absorb the force. The force literally exceeds the muscle’s strength, leading to a strain or a tear, commonly seen in the hamstrings or calves.”

Does this apply in Pulisic’s case?

We cannot know for sure, as Pochettino himself admitted, but the change in temperature, from Austin to Denver, was marked – around 20C (68F), according to the USMNT head coach.

Players stayed in Austin after the Ecuador game last Friday, before making the 2hr 15mins flight to Denver later on Saturday. According to AccuWeather, temperatures in Austin had reached a high of 33C (91F) and had lows of 21C (70F) on October 10; in Denver four days later, highs reached 21C, with a low of 7C (44F) overnight.

It is common for players, especially in Europe, to compete in much colder conditions than that, but it still represents a significant difference which made preparation all the more important for Pochettino’s players.

Mauricio Pochettino was unhappy at his USMNT players being asked to change conditions so abruptly (Andrew Wevers/USSF/Getty Images)

“The solution is straightforward: keep the muscles warm,” adds Scott. “This means the pre-match warm-up must be longer and more intense to achieve and hold an optimal muscle temperature. We also advise players to wear good thermal base layers to slow down that dangerous heat loss.”

Are there other issues with playing games at altitude?

Pochettino, an international with Argentina during his playing days, will have regularly experienced football at high altitude.

The impressive home records of South American countries such as Bolivia and Ecuador are regularly ascribed to playing home games at altitudes which far exceed Denver.

Bolivia’s recent 1-0 victory against Brazil was played at El Alto Municipal Stadium, 4,150m above sea level; Colorado’s DSG Park is a relatively lowly 1,584m, but that still makes it the highest stadium used in Major League Soccer, and significantly more elevated than Austin, where altitude ranges from 130m to 305m. 

It was clearly a concern for Pochettino to see his players being asked to make major readjustments for a friendly fixture.

“The impact of altitude on a footballer is major,” says Scott. “It’s a physiological shock, and the resulting fatigue is the main pathway to injury.

“At altitude (typically above 1,500 meters), there’s a state of hypoxia, meaning there’s less oxygen pressure driving oxygen into the player’s blood. This dramatically cuts their aerobic power.

“The biggest performance challenge is not the first sprint, but the player’s ability to recover from it. When recovery is compromised by low oxygen, the player enters a rapid state of severe fatigue as the match progresses. That exhaustion leads to a lack of mechanical control. A simple, misjudged step or a stumble because of fatigue can easily turn into a severe, acute injury like an ACL tear or an ankle sprain.”

USMNT defender Chris Richards acknowledged the difficulty after the game.

“Oh man, I’m dead. I’m dead. Even yesterday in training, we were dying,” Richards said. “But, gotta do it.”

Could this be an issue at the World Cup?

Denver is not among the host cities for the 2026 World Cup and none of the venues selected from the U.S. or Canada can be considered to be at high altitude.

Two of the three in Mexico, however, could raise issues. Mexico City, home to Estadio Azteca, is 2,240m above sea level, while Guadalajara is around 1,500m.

The impact of playing games at altitude was noted at the 1970 and 1986 World Cups played in Mexico and teams drawn into Group A of next summer’s tournament could be asked to quickly readjust between games played in Mexico City and Atlanta.

The challenges will then remain through the rounds of 32 and 16, when Mexico City will host its final game of the tournament on July 5.