Ivo Karlovic has seen off John Isner in a tense encounter to advance to the second round of the Mexican Open.

Karlovic, 34, got off to a great start when he broke the American in the first game. The match then went with serve until Isner showed his battling qualities to break back.

A tie-break was needed to settle the first set, and Karlovic raced into a 5-2 lead. Despite Isner winning the next two points, Karlovic managed to secure the set 7-6(4).

The second set went with serve, which meant another tie-break. Isner started poorly, losing his serve early on, and soon found himself facing match point.

Karlovic failed with his first two attempts, but eventually got the crucial point to confirm a 7-6(4) 7-6(5) victory.