Bernard Tomic has leveled the Davis Cup tie with the USA at 1-1, with a four set win over world No.24 Jack Sock.
Tomic recovered from a third-set lapse to win 7-6, 6-3, 3-6, 6-4.
The world No.20 looked set for a straight sets win, before Sock fought back to take the third set.
However, Tomic was able to grab the decisive break in the fourth at 4-4, before serving out the match.
Earlier, John Isner gave the USA a 1-0 lead with a 7-6, 6-2, 6-2 win over big serving Aussie Sam Groth, who played in place of Nick Kygrios, who withdrew from the tie due to injury.
John Peers and either Sam Groth or Lleyton Hewitt will taker on Mike and Bob Bryan in the all important doubles rubber tomorrow afternoon.