American John Isner hopes to have inflicted a telling mental blow to Australia’s Davis Cup hopes following his sweeping win over Sam Groth.

Isner was tested early by Groth, who was elevated to singles duty after Nick Kyrgios was ruled out of the World Group first round tie with a severe virus.

But after taking the first set in a tiebreak on Friday, Isner grew in confidence and cruised through the remaining sets to win 7-6 (7-2) 6-2 6-2 in under two hours.

It extended Groth’s miserable record in 2016, only managing one win, in the first round of the Australian Open, against seven losses.

While the opening singles was played in searing conditions on the temporary grass court at Kooyong, Isner said his win could cause more mental than physical damage to the Australian.

“Physically I think Sam will be fine,” world No.11 Isner said.

“At this point for me and him, it’s not a physical matter, it’s probably a bit more mental.

“Any time you win a match in a situation like this you’re on cloud nine and you feel like you’ve got a lot of confidence but on the flip-side maybe not so much.”

Davis Cup captain Lleyton Hewitt replaced Kyrgios in the four-man team and could join with Peers in the doubles or play singles on Sunday.

Groth is currently down to play doubles with debutant John Peers on Saturday against powerhouse paring Mike and Bob Bryan.

But teams are permitted to change players up to an hour before play.

The world No.77 said while he didn’t serve as well as he’d hoped against Isner he wanted the opportunity to face the Bryans.

“My body feels good and I feel like I’ve played good doubles in Davis Cup in the past and John and I have been playing well in practice,” said Groth.

“But it will be up to Lleyton.

“I will be doing everything I can to put my hand up to play.”