"It wasn't a loss for me, it was a win and a learning experience." -- Serena Williams, after being upset by Roberta Vinci at the US Open
Is there anyone who can touch Serena Williams' dominance? After completing her second aptly titled Serena Slam (consecutive wins in the 2014 US Open, 2015 Australian Open, 2015 French Open and 2015 Wimbledon), the tennis icon set her sights on a calendar Grand Slam: winning all four majors in one calendar year.
Even when she was down -- she had the flu on the way to her third French Open title -- her spirit and ground strokes seemed unstoppable, her serve almost unanswerable.
She lost to Roberta Vinci in three sets in the semifinals of the US Open, surprising everybody.
Still, Serena finished her amazing year ranked No. 1 -- the third consecutive time she's landed at the top of the world -- and there's no doubt that Williams, at age 34, will keep on slammin'.
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The IMPACT25 is espnW's annual list of the 25 athletes and influencers who have made the greatest impact for women in sports. Explore the 2015 list at espnW.com/IMPACT25.