Wimbledon 2015: Serena Williams completes the 'Serena Slam'

Serena Williams beat Garbine Muguruza 6-4, 6-4 on Saturday for her sixth Wimbledon title, and fourth Grand Slam championship.

Serena Williams of the United States returns a shot to Garbine Muguruza of Spain during the women's singles final at the All England Lawn Tennis Championships in Wimbledon, London, Saturday July 11, 2015.

(Sean Dempsey/Pool Photo via AP)

July 11, 2015

Game. Set. Serena Slam.

Serena Williams overcame a slow start, eight double-faults and a nervy finish to beat Garbine Muguruza 6-4, 6-4 on Saturday for her sixth Wimbledon title, fourth Grand Slam championship in a row and 21st major overall.

The win means Williams holds all four Grand Slam titles at once — completing the second "Serena Slam" of her career. What's more, she secured the third leg of a calendar-year Grand Slam and, if she wins the U.S. Open, will become the first player to sweep all four majors in the same season since Steffi Graf in 1988.

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Williams, winning her 28th straight Grand Slam match, is now just one major title behind Graf on the Open era list and two behind all-time leader Margaret Court Smith.

At 33, Williams is also the oldest women to win a Grand Slam title in the Open era. She has now won seven major championships in her 30s.

From 4-2 down in the first set, Williams ran off five straight games to take the set and go up 1-0 in the second. She pulled out to a 5-1 lead and twice served for the match but couldn't convert.

Williams was broken at love for 5-2, and Muguruza saved a match point and converted on her fifth break point to draw within 5-4. But Williams then broke the 21-year-old Spaniard at love to close out the match, which finished with Muguruza hitting a forehand wide.

As The Christian Science Monitor reported, Serena won her first "Serena Slam" between 2002 and 2003 when she won the French Open, Wimbledon, the US Open, and then went on to take the Australian Open crown in early 2003.

Forbes says Williams is “arguably the most dominant player in the history of…tennis.”  And while no one can argue that her 20 Grand Slam titles ensure her a revered spot in tennis history, Williams is part of a larger legacy.

Roger Federer, a Swiss player currently ranked No. 2 on the men's side, holds the record for most Grand Slam titles won by a male player, with 17 titles and holds the highest number of games won in Grand Slam tournaments at 290.  

Williams and Mr. Federer have often been compared by the media. Bleacher Report said they’re in the “’Grand Slams or bust’ phase” of their careers and other outlets have called them “the tennis twins.” But Williams has three more Grand Slam titles than Federer and is a seeded No. 1 player to his No. 2 status.