Defending champion Serena Williams laboured into the third round of Wimbledon by coming from a set down to beat fellow American Christina McHale in a thriller on Centre Court.
The world number one was in danger of suffering a sensational defeat in round two on Friday, but battled back to win 6-7 (7-9) 6-2 6-4 and set up a meeting with Annika Beck.
Williams, aiming to equal Steffi Graf's Open Era record of 22 grand slam titles, was pushed to the limit as McHale punched above her weight and will surely have to raise her game in order to win a seventh title at the All England Club.
The top seed was given a warning when she lost her temper after the 65-ranked McHale won the first set, but regained her composure to ensure she did not follow second seed Garbine Muguruza out of the exit door at SW19 despite making 40 unforced errors.
Williams made a sluggish start, paying the price for three unforced errors as she failed to hold in the first game and McHale showed admirable defiance to fend off four break points to take a 2-0 lead.
The world number 65 was unable to win a break point which would have given her a 3-0 advantage, but was unperturbed and executed a delicate drop shot to make it 3-1.
Williams continued to make uncharacteristic errors, but she saved a further three break points and levelled at 4-4 with a rasping return winner before a short suspension when the rain returned.
The underdog saved a set point in the 10th game and twice battled back from a mini-break down in the tie-break to take the opening set, leaving a furious Williams rattled as she hammered her racket into the turf.
Williams was given a warning by the chair umpire and booed by the crowd for that tantrum, but channelled her frustration effectively in order to level the match in emphatic fashion after breaking twice.
McHale hit back by taking a 2-0 lead in the decider, but tossed away her advantage with two double faults to gift the break back to her compatriot and had to dig deep to save a further four break points in her next two services games.
The crowd were on their feet to show their appreciation for an epic rally won by McHale, but Williams got the break in that game to lead 5-4 and showed her relief after serving out the match to stay in the hunt for a first major since winning Wimbledon last year.