Third seed Novak Djokovic survived a gruelling examination to reach the quarter-finals of the U.S. Open on Tuesday, beating Argentine Juan Monaco 7-5 7-6 6-7 6-1 in an absorbing encounter.
The Serb was pushed to the limit in a match of exhausting rallies as Monaco saved a match point in the third set before wearing down the Argentine in three hours, 53 minutes.
Monaco had never won a match at the U.S. Open before this year and when Djokovic broke to lead 2-0 in the first set it looked like the Serb would have an easy win.
But the 23rd seed played some inspired tennis to force Djokovic to dig deep, saving the match point before winning the third set on a tiebreak.
An early break in the fourth set put Djokovic on his way, though, and he eventually wore Monaco down to set up a clash with veteran Spaniard Carlos Moya.