Melbourne (AFP) - Captain Jim Courier said the heavyweight Bryan brothers doubles pairing gave the United States the edge over Australia in their Davis Cup tie with the scores locked at 1-1 after the opening singles matches on Friday.
Australia's Bernard Tomic beat Jack Sock to level the World Group round one tie between the great, traditional Davis Cup rivals after John Isner breezed past Sam Groth in the first match.
Tomic rolled through the opening two sets against Sock before being forced to battle hard to win 7-6 (7/2), 6-3, 3-6, 6-4 in sweltering conditions at the famous Kooyong centre court in Melbourne.
The victory, in sweltering temperatures, was crucial for Lleyton Hewitt's Australians, after world number 11 Isner trounced the 77th-ranked Groth 7-6 (7/2), 6-2, 6-2.
The retired Hewitt is on standby for a possible playing appearance following the match-eve withdrawal of star youngster Nick Krygios with a virus and back trouble.
Courier, who works as a television commentator alongside Hewitt at the Australian Open, said he was confident America held the whip hand with doubles specialists Bob and Mike Bryan, who are multiple Grand Slam champions.
"Bob and Mike seem to be at an advantage in the historical count of doubles in Davis Cup, but every day is a different day," Courier said.
"They?ve played awfully well. We feel confident in them, but we don?t take anything for granted. We?ll be ready to go -- but I love having them on our side."
Hewitt, in his first Davis Cup as captain after retiring at the Australian Open in January, was giving little away about his selection options for the doubles, even about his own chances of playing a role.
"The Bryans obviously are the favourites tomorrow in the doubles. But I still think our guys have got a good shot at it, and then on the last day anything can happen."
Hewitt has until an hour before the doubles tie to finalise his combination and choose between the team's doubles specialist John Peers, Groth and himself.
Earlier Tomic, ranked 20, sent tremors through the Australian camp when he hit a flat spot during the third set of his tie, inviting world number 24 Sock back into the match and a fourth set.
But Tomic rallied and broke the American in the ninth game and served out for a four-set win on the grass of Kooyong, former venue for the Australian Open.
"It was very tough out there. I haven?t beaten Sock before so I knew that it was going to be tough," Tomic said.
"But playing him on a (grass) surface where I could beat him on I was very happy because the conditions were very tough."
Earlier Isner's serve was too strong for Groth and he wrapped up the contest in one hour 49 minutes.
Isner served his way out of three break points down in the first set to confidently take the opening set in a tiebreaker 7-2.
The beanpole American smashed 20 aces as Groth's game deteriorated and posed an early selection dilemma for new Australian captain Hewitt.