KEY BISCAYNE, Fla. — Venus Williams sagged in the wooden changeover chair as if it were a cushy recliner, her head tilted back, her tank on empty.

KEY BISCAYNE, Fla. — Venus Williams sagged in the wooden changeover chair as if it were a cushy recliner, her head tilted back, her tank on empty.

She rose slowly to play the final two games and lost both, but grinned as she walked to the exit, perhaps because she was headed for a well-deserved rest.

Weary after winning three consecutive three-set matches, Williams was eliminated Wednesday by Agnieszka Radwanska in the quarterfinals of the Sony Ericsson Open, 6-4, 6-1.

Top-ranked Victoria Azarenka lost for the first time this year when she was beaten by Marion Bartoli, 6-3, 6-3. Azarenka had won 26 consecutive matches, a streak that dated to the beginning of 2012.

In the men's quarterfinals, No. 2-seeded Rafael Nadal continued his bid for his first Key Biscayne title by beating No. 6 Jo-Wilfried Tsonga 6-2, 5-7, 6-4. His opponent Friday will be 2009 champion Andy Murray, who overcame an upset stomach and early deficit to beat No. 9 Janko Tipsarevic 4-6, 6-3, 6-4.

Williams' serve lacked its usual velocity, and by the final game she wasn't even chasing shots in the corner. The tournament was her first since the U.S. Open last August, when she withdrew after being diagnosed with a fatigue-causing autoimmune disease.

Eager to keep points short in the 85-degree sunshine, Williams charged the net often but frequently had to lunge for shots. She committed 38 unforced errors to 10 for Radwanska, and won only five of 26 points on her second serve.