Marin Cilic believes that his service performance helped him to advance through to round four of the US Open at the expense of Kei Nishikori earlier today.

World number 13 Cilic raced into a two-set lead, before he was pegged back by his Japanese opponent during a third-set tie-break.

However, the Croatian responded in the fourth set with a string of aces, which allowed him to book his place in the next round.

"I served well. I think that was the key," Cilic told reporters. "He played really well in the tie-breaker. We both had a lot of chances in the match."

Cilic will now take on Martin Klizan for a place in the quarter-final.