Stanislas Wawrinka overcame a third-set wobble to beat Illya Marchenko and claim a place in the quarter-finals of the US Open in New York.
The third seed, who has lost two semi-finals at Flushing Meadows, earned a 6-4 6-1 6-7(5) 6-3 triumph in two hours and 48 minutes.
Wawrinka battled to save two break points on his opening service game before going a break up himself early in the first set.
Marchenko posed a threat as he eventually broke back, but the two-time Grand Slam champion regained composure to snatch serve for a second time to win the opener in 46 minutes.
The second set was more comfortable for Wawrinka as he wrapped it up in just 22 minutes, while his opponent failed to create a single break point.
Last year's semi-finalist needed to serve for the match to clinch a spot in the next round, but Marchenko broke to provide a tense finish.
After forcing the contest into a fourth set, the Ukrainian put Wawrinka on the backfoot by snatching serve, but the Swiss player responded with a double break and eventually saw out the set to grab a place in the final eight.
