United States legend Kasey Keller says "the sky's the limit" for Chelsea winger Christian Pulisic.

The 21-year-old forward has excited Chelsea fans since the Premier League restart, scoring twice in three games.

Frank Lampard is excited about Pulisic's potential, and Keller agrees.

"I thought he was Chelsea's best player for the majority of the match," former Spurs and Leicester goalkeeper Keller told ESPN FC.

"What he's able to do in not just setting up other players but finding himself in goalscoring opportunities, [Kasper] Schmeichel made a brilliant save or he would have scored in the first half.

"If Pulisic can stay healthy and continue to learn and play better, there's no question I completely agree with Frank that the sky's the limit.

"You've seen that from him this season already. Alright, it's been stop-start, he's had a few injury issues, but now he looks to be back at full form.

"His ability to on the turn skate past defenders and create space for his team going forward and create goalscoring chances not just for himself but for his team-mates, that's a rare gift.

"Like I said, the sky's the limit."