Serena Williams continue to keep alive her hopes of a record-equalling 24th Grand Slam singles title with a 4-6 6-3 6-2 win over Tsvetana Pironkova in the US Open quarter-finals.
Williams struggled early on with the variety of shots from the unranked player who was in her first tournament in three years.
Has with earlier matches, Williams made a slow start which Pironkova exploited with longer rallies and with her dangerous sliced forehand.
There were signs Williams was improving towards the end, as she out-thought and out powered her opponent in the eighth game, decided by an error following a phenomenal 26-shot rally.
It was smooth sailing on serve for the American for the rest of the day, only dropping two further points on her delivery.
In paying tribute to Pironkova for reaching the last eight, Williams stated:
“It shows me how tough mums are,” the former champion said. “Whenever you can birth a baby, honestly you can do anything. We saw that today, she played unbelievable.
“I could barely win a match when I came back, so she’s incredible. Her baby has to be younger than mine – you play a match, go home and you’re still changing diapers, it’s like a double life.“
Williams will now play former world number one Victoria Azarenka or Belgian 16th seed Elise Mertens.