Victoria Azarenka, the No. 2-ranked women's tennis player in the world, took a scary spill on Day 1 of Wimbledon today, injuring her right knee but still managing a victory over Maria Joao Koehler in straight sets (6-1, 6-2).

After taking the first set, Azarenka was up 1-0 before slipping and falling to the ground. She was seen crying in pain as she received medical attention, and stayed to finish the match with a heavy wrap on her right knee. As she played, Azarenka noticeably limped and winced a few times.

Azarenka's mobility will likely be limited for the remainder of Wimbledon, and it is unclear if she will be able to battle through the injury in order to take the court against Flavia Pennetta in the second round.

In other Wimbledon news, fifth-seeded Sara Errani, who reached the finals of the French Open semifinal round against Serena Williams, was upset by 19-year-old Puerto Rican Monica Puig 6-3, 6-2.

Puig, who showed incredible striking, topped the heavy favorite in her first-ever all-grass tournament appearance. Errani has gotten to the semifinals or further in three of the last five Grand Slam events, so her ouster comes as a major surprise.

While Errani has a proven track record in Grand Slams, she also has a history of underperforming at Wimbledon. Last year at Wimbledon Errani lost her first set to Yaroslava Shvedova in humiliating fashion, failing to register a single point. That golden set was the first in Grand Slam history.

On the men's side, No. 3 Roger Federer took care of business in straight sets 6-3, 6-2, 6-0 against Victor Hanescu, the world's No. 48. No. 10 Marin Cilic also was victorious in his Wimbledon opener, winning 6-3, 6-4, 6-4 over Marcos Baghdatis.