New York, Aug 26 (IANS): No.13 seed Maria Sakkari delivered a brilliant performance as she came from the brink of defeat to shock two-time champion Serena Williams and roar into the quarterfinals of the ongoing Western & Southern Open.

Sakkari, who started the week with a decisive victory over American teenager Coco Gauff, trailed by a set and a break in her first meeting with the 23-time Grand Slam champion only to roll through the final set after two hours and 17 minutes to win the match 5-7, 7-6(5), 6-1 on Tuesday evening.

"I haven't realised it yet," Sakkari said after the match as per the WTA website. "It feels pretty good, because she (Williams) has been a role model for me growing up, and obviously what she has achieved is huge. So it feels very nice."

"I was not feeling good. This first set and a half, I could not feel my shots. There were some points where I was playing good, but I knew it was going to be ugly.

"I'm kind of proud of myself that I came through that match just because of my mentality and my fighting spirit," she added.

The No.13 seed made two more winners (27 to 25) and 15 fewer errors (43 to 58), converted five of 19 break point opportunities while maintaining a 59 per cent first-serve percentage, striking seven aces to Williams' nine.

"It was tough," Williams said after the match. "I literally should have won that match. There was no excuse. It was hard, but I had so many opportunities to win, and I have to figure that one out, like how to start winning those matches again. There is really no excuses, to be honest."

Sakkari will now face British No.1 Johanna Konta for a place in the semi-finals.