She was staring at a third-round exit in Melbourne but Venus Williams responded to progress at the first grand slam of the year.
Venus Williams rallied to overcome Camila Giorgi and advance to the Australian Open's last 16 on Saturday.
The American 18th seed looked down and out, trailing by a set and staring at a 5-2 deficit in the second.
But she fought her way back to claim a 4-6 7-6 (7-3) 6-1 win over powerful Italian Giorgi on Margaret Court Arena.
Giorgi led 4-2 in the second set and had Williams serving at 0-40 but she failed to capitalise.
While Williams reached the fourth round of a major for the first time since Wimbledon in 2011, Giorgi finished with 16 double faults and 62 unforced errors.
Williams struggled to find her range early and Giorgi, whose depth kept her in points, broke for a 2-1 lead.
However, Giorgi served two double faults in the next game and Williams broke back with a backhand cross-court winner return.
Giorgi's flat hitting helped her break again for a 4-3 advantage.
The pair went toe to toe from the baseline and Giorgi was winning most of the powerful exchanges.
Giorgi needed six set points to take the set but a body serve saw her do so in the 10th game.
She broke in the opening game of the second set when Williams sent a backhand well long.
Williams was back on level terms in the fourth game, breaking serve as Giorgi battled her ball toss " serving two double faults.
However, Giorgi broke once more to lead 3-2 " and then battled from 0-40 down to consolidate.
That appeared to be the end for Williams, who maintained hope when she recovered from 0-40 down in the seventh game thanks to some Giorgi over-hitting.
Williams made Giorgi serve it out, and she was unable to " broken to love to see the set level at 5-5.
Giorgi saved two set points in the 12th game to force a tie-break.
A fine forehand cross-court passing shot from Williams gave her a 4-2 lead in the tie-break on the way to forcing a deciding set.
Giorgi sprayed a backhand long and wide to see Williams break in the first game of the third set.
Williams had chances to go up a double break but Giorgi held serve after a marathon 28-point third game.
A second break would come, however, thanks to Giorgi's faltering serve and a forehand down-the-line passing shot.
From then, Williams was untroubled as she closed out victory.