Serena in US Open QF after beating Estonia's Kaia Kanepi

Serena Williams has reached the quarterfinals at the US Open in Flushing Meadows here after beating Estonia's Kaia Kanepi  6-0, 4-6, 6-3.

Williams had a tough time on Sunday with Kanepi, even after starting out firmly in control. In the second set she nearly battled for her life before ultimately putting down her opponent, Efe news reported.

This marks the 10th consecutive time that Williams has reached the quarterfinals at the annual tourney, although she did not play in 2017 when she took time off as she became a mother.

"It wasn't an easy match at all. (Kanepi) obviously knows how to play," Williams said. "I was just happy to get through it."

Williams dominated in the first set, routing Kanepi 6-0 in just 18 minutes.

However, after clearly dominating in the first set, taking 24 out of 30 points, firing 14 winners and committing only two unforced errors, Williams seemed to lose her focus as the 44th-ranked Kanepi overcame her initial tightness.

It was Kanepi who had eliminated the No. 1-ranked Simona Halep of Romania on the first day of the Open, and she has made it to Grand Slam quarterfinals about half a dozen times.

With Williams faltering, Kanepi came on strong, returning her rival's serves especially well and boring in as the American continued to make unforced errors to take the second set 4-6 after both players broke each other's serve once.

In the third set, in another momentum shift, Williams appeared to settle down again, moving through the games relatively well for the 6-3 result to take the match and earn her ticket to the quarterfinals.

The set Williams lost to Kanepi was the first one to get away from her  at the 2018 US Open, including in the 6-1, 6-2 win over her older sister Venus on Friday.

Williams will now go up against Karolina Pliskova in the quarterfinals, after the Czech player defeated Australia's Ashleigh Barty 6-4, 6-4 earlier on Sunday.