'Kill mode': Serena Williams' brutal act in US Open 'shock'

Serena Williams has left tennis fans in a frenzy after storming back from a second round scare against an American teenager to seal her place in the next round of the US Open.

Having destroyed Maria Sharapova in her first round win, Williams struggled to find her best form against 17-year-old American Caty McNally, before steadying to claim a 5-7 6-3 6-1 victory on Arthur Ashe Stadium.

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The 23-time grand slam champion, who has never lost in the US Open second round, eventually powered through the final set against McNally, dropping just five points.

Williams will face either Hsieh Su-wei or Karolina Muchova in the third round after surviving the McNally test.

Serena Williams bounced back from a disappointing opening set in trademark fashion. Pic: Getty

Fans were beside themselves after McNally took the opening set against the 23-time grand slam champion, with many sniffing a potentially massive upset.

Typifying exactly what makes her the champion she is though, Williams bounced back in style to take out the second set with relative ease.

The 37-year-old claimed 12 of the final 16 games of the match to extinguish any hopes of an upset that her young opponent held.

Williams rode a wave of momentum to steamroll her inexperienced opponent in a clinical deciding set.

The six-time US Open champion raced out to a 4-0 lead before McNally finally stemmed the bleeding to claim a game.

The World No.121 had no answer to the Williams onslaught, however, as the veteran American closed out the third set 6-2 to seal her place in the third round.

Williams does it the hard way

So impressive in the first round thrashing of Sharapova, Williams struggled to find the same form and dropped serve in the 11th game, a huge forehand return helping McNally take a 6-5 lead.

McNally then came from 0-40 down when serving for the opening set, which the teenager clinched with a huge serve.

Caty McNally was on fire in the first set. Pic: Getty

After an even start to the second set, Williams broke in the sixth game with a forehand return winner, although she was challenged before consolidating for 5-2.

Williams seemed to be settling and levelled the match with a huge ace and a volley winner from 30-30 in the ninth game.

And, Williams quickly struck in the third set, breaking to love in the opening game after another big forehand return.

She won 16 of the first 17 points of the final set, setting up a huge lead to power through.

"She really came out and played really well, she showed no fear," a relieved Williams said in her on-court interview.

"She had absolutely nothing to lose and she played like it.

"I am not too pleased with the way I played at all," added Williams, whose 28 unforced errors were two fewer than McNally’s.

"But it's OK, I'm alive, I'm still here and happy to be on this court. I'll do better. I promise."

With agencies