Serena Williams has sent tennis fans into a frenzy after setting a new Open era record for most comeback victories after losing the first set.
Serena came out on top in the battle of the supermums, rallying back from a set and a break down to defeat Tsvetana Pironkova and reach her 14th US Open semi-final on Wednesday.
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In a historic showdown between two mothers, the 38-year-old Williams posted a 4-6 6-3 6-2 win over Pironkova.
Serena is now 44-42 when dropping the first set at grand slams, the most come-from-behind wins in the Open Era.
The 38-year-old is chasing a 24th singles grand slam title that would equal Margaret Court's record.
But a sluggish start to the match almost saw her hopes dashed as a more energetic Pironkova broke Williams in game five to take an early lead.
“I'm happy to be standing here talking to you because at one point I think I was pretty close to not being here,” Williams told an on-court interviewer.
“I keep fighting and that's one thing that I'm super excited about. I never give up and you know I just gotta keep going,” she added.
Williams blamed her early struggles on tiredness.
“I was feeling a little in my legs and for whatever reason an hour in I get more energy so I guess that's a good thing,” said Williams.
“In the beginning I was a little fatigued for whatever reason so obviously I can't do that if I want to keep winning.
“So I'm going to try to figure that out,” she added.
Tennis fans erupted over Serena’s ‘insane’ fightback.
Of all the insane GOAT stats of Serena’s career, this one is especially bonkers https://t.co/i6cJiKp1RD— Kaiser@Celebitchy (@KaiseratCB) September 9, 2020
Serena still serving at 200 km/h after 2 hours and 20 minutes lol, that's just insane— Artikodin/Cyndakill (@Artikodin25) September 9, 2020
My Heavens this is spectacular from Serena. I just can't believe she's been playing as long as I've been a professor. It's crazy.— BadToss (@BadToss) September 9, 2020
Certain athletes are just special. I can’t believe Serena just did this. 👊🏻 pic.twitter.com/AS4USIOxlQ— HoopMedic -Russel Deverteuil (@Hoopmedic) September 9, 2020
Serena praises ‘unbelievable’ Pironkova
It has been more than three years since Williams won her 23rd grand slam title at the 2017 Australian Open - when she was already pregnant with daughter Olympia.
Williams has come close since, reaching four major finals only to come away empty handed.
Pironkova, herself a mother, only returned to tennis this year following a three-year absence from the circuit.
“Whenever you can birth a baby honestly you can do anything and I think we saw that with Tsvetana today. She played unbelievable,” said Williams.
Pironkova's last tournament appearance before this year's US Open had been the 2017 Wimbledon championships when she exited in the second round.
She gave birth to her son during her break from tennis but elected to return in 2020, only to see her comeback plans disrupted by the coronavirus shutdown.
Williams said she was in awe of Pironkova's run to the last eight.
“I couldn't even do that. I could barely win a match when I came back so she's incredible,” she said.
“It's like you play a match and you go home and you're still changing diapers. It's like a double life, it's really surreal.”
Williams smashed 20 aces, taking her tally for the tournament to 64 so far.
The record for the most number of aces in a US Open in the women's singles is 70, set by Serena in 1999 when she won for first time.