Key Biscayne (Florida): Venus Williams`s comeback from an energy-sapping illness ended with a 6-4, 6-1 defeat to Poland`s Agnieszka Radwanska in the quarter-finals of the Sony Ericsson Open on Wednesday.
Williams, playing in her first singles tournament since her shock withdrawal from last September`s US Open with Sjogren`s Syndrome, said her late-night match against Ana Ivanovic on Monday had taken its toll.
"I was up until like 4 a.m. recovering from the match and all the things that you have to do after," said Williams. "So the next day I think I should have rested more."
The auto-immune disease causes fatigue and joint soreness and, after doing well to reach the last eight by outlasting Ivanovic in three sets, Williams looked sluggish in the latter stages of Wednesday`s 80-minute match.
World number four Radwanska enjoyed a 74 percent first serve percentage while Williams, who entered the tournament as a wildcard, paid the price for 33 unforced errors.
Williams, however, was encouraged to have made it to the last eight in her first tournament back.
"This is definitely a start," said Williams, whose sister Serena was eliminated by Caroline Wozniacki on Tuesday, "I`ve definitely learned a lot about ways that I could prepare during the tournament."
Radwanska, who won in Dubai in February, will face either top seed Belarusian Victoria Azarenka or France`s Marion Bartoli who play their quarter-final later on Wednesday.