A "sluggish" and "tired-looking" Serena Williams struggled past Lucie Safarova in three tough sets at the Hopman Cup in Perth, Australia on Thursday, but insisted she felt "really good."

Conflicting reports surfaced Thursday after Williams' 6-3, 6-7 (1), 7-6 (6) victory over Safarova maintained questions Williams' health less than two weeks before the Australian Open.

Serena Williams claims fatigue in opening match of Hopman Cup

Williams gave the United States a 2-0 lead in the mixed-team event. Her partner, John Isner, defeated Adam Pavlasek 7-6, 6-2.

Reuters' report indicated a Williams fighting through fatigue to push her team forward in the Hopman cup.

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"I just never give up," a tired-looking Williams said in a courtside interview, according to Reuters. "I've been through so much in my life on the tennis court. I just keep fighting and keep doing the best I can."

The Guardian, however, reported that Williams' condition has improved significantly since her 6-2, 6-1 loss to Canadian Eugenie Bouchard in the first of the matches at the Hopman Cup.

"I have an ache here and there, but physically I feel like I can run a 10K," Williams said. "It feels so much better than I did a couple of days ago. I feel really good now.

"I feel like I'm getting back in the groove. I'm not moving as well as I was last year. But I'm going to try to improve that. I know I can. I'm getting there."

Williams' episode at Wimbledon last summer raised concern about both her physical and emotion condition in July. Serena couldn't bounce a ball with her racket consistently and failed to get a serve over the net.

She said she was just sick during that time. Williams bounced back to win both the U.S. Open - for her 18th Grand Slam title - and the season-ending WTA Finals in Singapore.