Top-ranked, top-seeded Serena Williams staged an extraordinary final set fightback to beat Britain's Heather Watson 6-2, 4-6, 7-5 in the third round of women's singles at Wimbledon on Friday to set up a blockbuster fourth-round showdown with sister Venus.
Williams, bidding for a sixth Wimbledon title and a calendar Grand Slam, was on the brink of a dramatic third-round exit when Watson served for the match at 5-4 in the final set. But Serena, who had trailed 3-0 in the decider, showed why she has won 20 Grand Slam titles as she broke back before finally sealing an epic escape in two hours and 14 minutes in front of an enthralled 15,000-strong crowd on Centre Court.
Serena's 53 winners and 13 aces were just enough overcome her 33 unforced errors in the match of the tournament to date.
"I've had some tough losses but that was probably my toughest match, playing Heather in front of her home crowd," Williams said. "She played unbelievable and really I think she should have won the match.
"She was up two breaks and she just really gave her all and showed us what a great player she is."
The 33-year-old American will face 16th seed Venus on Monday for the first time in a Grand Slam since beating her in the 2009 Wimbledon final. The sisters' last meeting came in 2014 when Venus won in Montreal, but Serena holds a 14-11 advantage over the 35-year-old in their career head to head.
They have clashed five times previously at Wimbledon, with Serena winning three times and Venus twice.
"Venus is in better form than I am, so I think she has a little bit of an advantage going into that match. But at least one of us will be in the quarter-finals, so that will be good," Serena added.
Faced with the prospect of a third successive early departure from Wimbledon, Serena had to dig deep to keep alive her hopes of becoming the first woman since Steffi Graf in 1988 to win all four Grand Slams in the calendar year.
The gritty recovery extended her winning streak in the majors at 24 matches -- a blistering run that started after her third round loss to Alize Cornet at Wimbledon 12 months ago and has brought her the 2014 US Open crown and titles at the Australian and French Opens this year.
While Serena breathed a sigh of relief, world number 59 Watson departed to a standing ovation after narrowly failing to become the first British woman to beat a reigning world number one since Sue Barker defeated Chris Evert in 1979.
Watson had a poster of Serena on her bedroom wall as a tennis-mad child growing up in the Channel Island of Guernsey. But the dream of facing her idol initially turned sour as Watson was overpowered in the first set, with the American breaking in the fourth game and again in the eighth to take the lead in just 25 minutes.
But Williams, facing a Briton at Wimbledon for the first time, appeared rattled by Watson's tenacity and the fervour of the crowd's support for their compatriot in the second set. A series of miscues from the increasingly anxious Serena allowed Watson to break at 4-4 and she couldn't stop the Briton levelling the match.
It was the first set Serena had dropped in the tournament and another stream of errors gave Watson two breaks for a scarcely believable 3-0 lead in the final set.
Crucially, Serena stopped the bleeding with a break in a marathon 10-minute fourth game and she broke again to level at 3-3.
Remarkably, Williams stumbled again at 4-4 as Watson battled her way to another break. But Serena refused to surrender and she broke back at the fourth attempt when Watson served for the match.
That set the stage for a sensational finale as Watson staved off two match points at 6-5 before Serena finally completed her great escape.