Dimitrov scrapes into Open third round

World No.3 Grigor Dimitrov has survived a mighty scare to safely progress to the Australian Open third round at Melbourne Park.

Dimitrov battled past unheralded young American qualifier Mackenzie McDonald 4-6 6-4 6-2 0-6 8-6 in an epic encounter that finished at almost midnight on Wednesday.

Mackenzie had never even won a tour match until Monday, but threatened to pull off the upset of the tournament after delivering the Bulgarian third seed a fourth-set bagel.