Miami - Serena Williams looks all but certain to withdraw form next week's small debut clay event in Marbella, Spain, after a thigh injury contributed to a 6-3, 6-1 loss in the Miami Masters final.

The five-time winner at the venue lost to Victoria Azarekna 6-3, 6-1, her left thigh heavily strapped and her movement compromised.

"I thought about not playing but I thought the warmer I got the better it (might be)," said the 10-time Grand Slam champion. "It was hurting probably in my quarter-final, and it just progressively got worse.

"It was a little difficult moving to the left and a little bit to the right ... forward was also difficult."

Williams is entered in the tiny 220,000-dollar Marbella event, which she looks unlikely to play now.

"I should probably take a couple weeks off, I don't know, we'll see," she said.

The American said that despite failing to set a record with a sixth title in Miami, she remains "extremely motivated."

"Even when I was losing, I was thinking of things that I could improve on and things that I want to improve on for the next match and the next tournaments and the clay courts and grass courts and things like that."

Williams pronounced herself "excited to get on the clay."

"I want to keep working on fitness and consistency, obviously, which are the things going into clay."

Hours after the success, Azarenka was still taking it all in. "I was so happy, it was the biggest win of my career so far," she said. "I was just so happy to finish that match, because I was getting a little bit nervous in the end.

"I never think about the match until right before the warm up. I never do, so I wasn't thinking about it last night or today.

"That's why I probably don't get that nervous as maybe somebody else."

Azarenka said that while she might still be under-age, she will find a way to celebrate the biggest win of her career.

"I'm not allowed to drink in the States, yet, but I'll definitely go celebrate somewhere in the restaurant." (dpa)