Serena Williams spent the last five months of 2014 proving to tennis fans that she was the No. 1 women's player in the world, despite lukewarm results during the previous seven.

And in less than an hour in her second match of 2015, Williams has allowed questions about her game resurface.

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BBC.com reported that rising Canadian star Eugenie Bouchard scored her first-ever win over Williams at the Hopman Cup in thrashing fashion, a 6-2, 6-1 triumph in 50 minutes.

The match comes one day after Williams needed a shot of espresso during her match against Flavia Panetta to defeat the Italian 0-6, 6-3, 6-0.

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"I don't know what's wrong with me, I'm so tired," said the 33-year-old Williams after losing to Bouchard.

"It's weird. I can't get my body to move. I feel like I've got no energy. It's a little frustrating because I know I can play two thousand times better. I've been trying to rest up. I did a little gym work, but I just felt depleted. I don't know why. I don't know how to describe it. I've just got to get my feet moving. I have to figure it out. Hopefully I can do better in the next match."

The result is a continuation of a strange 2014 season for the game's top player. Williams did not advance past the fourth round of any of her first three Grand Slam events last year, and she appeared disoriented in a Wimbledon doubles match that raised serious questions about her health.

After her Wimbledon incident, Williams responded by winning two warmup tournaments leading to the U.S. Open and then did lose more than three games in any set at the season's final Grand Slam for her 18th major title.

But then Williams retired during the first set of her next match against Alize Cornet in Wuhan, China, then allowed Samantha Stosur win in a walkover during their quarterfinal match in Beijing.

Williams recaptured her U.S. Open magic at the season-ending WTA Finals in Singapore - for the most part. On her way out of the round-robin pool and a win over Caroline Wozniacki in the finals, she also suffered a 6-0, 6-2 loss to Simona Halep in the round-robin portion.

Days later, Williams beat Halep 6-3, 6-0 in the semifinals of the WTA event.

The dramatic swings in Serena's game raise questions over whether she is not 100 percent physically or whether lapses in focus are the cause of such a disparity in her results.