Serena Williams has booked her place in the Wimbledon semi-finals as her quest for an eighth singles crown at SW19 goes on.
The 23-time Grand Slam winner joins Simon Halep in the last four, though the two can't meet until the final having been kept apart by the draw.
Williams moved a set in front swiftly against Riske but surrendered her advantage as the latter broke nine games into an attritional second set.
Though Riske fought fiercely in her first Grand Slam quarter-final, it was Williams who advanced after a topsy-turvy decider.
The seven-time Wimbledon champion was broken early but roared back, twice breaking Riske's serve as she looked to see out the third set in double-quick time.
Riske then broke back as the Centre Court crowd buckled in for a marathon match, but the 29-year-old appeared to run out of puff as the set inched towards a conclusion.
Broken for a final time in a mammoth eighth game, Riske shut down three Williams break points before a fourth proved a bridge too far.
Williams will now contest her third Slam semi since giving birth in September 2017
