World Number one Serena Williams kept her bid for a calendar-year Grand Slam intact by outslugging older sister Venus 6-2, 1-6, 6-3 in a power-packed quarter-final at the US Open in New York.
Serena entered the match with a 15-11 head-to-head advantage over Venus but the high number of losses to her 35-year-old sibling represented the most posted by any opponent against the world number one, who knew she was in for a tough fight.
The 33-year-old top seed, winner of 21 Grand Slam singles titles, took charge of the opening set by securing service breaks in the fifth and seventh games of a match that felt like a heavyweight title bout after a brilliant start by Venus.
However, Venus looked more like the player who has claimed seven Grand Slam singles titles in the second set, unleashing her power and drawing groundstroke errors from Serena for two service breaks that sent the match to a third set.
Serena seized control early in the decider and rode the momentum to the finish in her quest to join Maureen Connolly (1953), Margaret Court (1970) and Steffi Graf (1988) as the only women to win Wimbledon and the Australian, French and US Opens in the same season.