Mardy Fish was made to work for his win against Kevin Anderson to make it through to round four of the US Open.

The American was at his most dominant in the first, where he was able to find a break to close out the set 6-4.

The second proved tougher, as the South African matched his opponent to take it to a tie-break, which Fish won 7-4.

There was little to seperate the two players in the third as it was decided again by a tie-break. This time Fish made slightly lighter work of Anderson, winning 7-3.

The eighth seed will play either Jo-Wilfried Tsonga or Fernando Verdasco in the next stage.