"I just got a bit of a kick in the first half so I'm really hoping that it's nothing. Taking a little bit of precaution today. But I'm hoping I'll be fine in the next few days," said Pulisic.

The AC Milan forward is the United States' talisman, carrying the hopes of the host nation as it looks to make history with a deep run on home soil.

Pulisic was a constant menace in a rampant first half, providing an assist and helping force Paraguay's own goal after a slick one-two with Weston McKennie.

However, he was withdrawn at the break and later told reporters he had suffered a knock to the back of his left leg.

"Sort of my calf area. But I've had similar things before. I'm staying positive. I don't think it's anything at all."

Coach Mauricio Pochettino said the forward was taken off because the team did not want to take any risks.

"He received a kick before today in a training session. We hope it's not a big issue. When he finished the first half, he could not walk.

"We're hopeful the next game he'll be available."

The United States return to action against Australia on Friday before facing Turkey the following week.

"An incredible start, but there's a lot more that we still have to do," Pulisic said.

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