Serena Williams has taken her tennis career to another level by winning four of the past six Grand Slam titles since teaming up with French coach Patrick Mouratoglou. And if she can duplicate that performance over the next six Grand Slams, the 31-year-old American star will be on the verge of matching Steffi Graf as the most prolific Grand Slam singles champion of the Open Era. World number one Williams captured her 17th career Grand Slam crown Sunday, defeating second-ranked Victoria Azarenka 7-5, 6-7 (6/8), 6-1 in the US Open final at Arthur Ashe Stadium, her fifth title on the New York hardcourts. Williams stumbled twice serving for the match in the second set but dominated the third to move another step higher on the Grand Slam honor roll. \"When you\'re always trying to write history, or join history in my case, maybe you just get a little more nervous than you should,\" Williams said. \"It\'s kind of cool. It means a lot to me, this trophy, and every single trophy that I have. It makes me feel that I\'m still fighting just to be a part of this fabulous sport.\" It follows her second career French Open title earlier this year on Paris clay and her Wimbledon and US trophies last year, all coming after she turned to Mouratoglou following a first-round crash out in last year\'s French Open. Williams has won as many Grand Slam titles as all-time men\'s leader Roger Federer and is one Slam title shy of matching Martina Navratilova and Chris Evert with 18 major titles. \"To be compared with Chrissy and Martina, not yet, because I\'m still not quite there yet,\" Williams said. \"I can\'t necessarily compare myself to them because numbers-wise they are still greater.\" Graf is on 22 Grand Slam titles with Margaret Court at the all-time record 24, but if Williams wins four of the next six major titles she would be on 21 and still have the 2015 Wimbledon and US Open to play before her 34th birthday. Williams is 98-5 since teaming up with Mouratoglou, who has added variety to her formidable power game and consistency to her baseline strokes, helping her cope with the pressure of being the world\'s top player with calm and focus. \"Every time she steps on the court with that pressure on her shoulders, it\'s an achievement also to be a winner at the end,\" Mouratoglou told USA Today. Following a 2010 foot injury, Williams developed blood clots in early 2011 that jeopardized her life and when she returned, she only went past the fourth round once in her next four Grand Slams, the last being the first-round French Open flop that led her to Mouratoglou. Williams, who has been romantically linked to Mouratoglou, says he helps her avoid letdowns and inspires her to play her best no matter the opponent. \"I think more than anything I would say just consistency and getting up for every match,\" Williams said when asked where he has helped her improve. Williams is so confident in her ability to win Slams these days that a fourth-round Wimbledon ouster by Sabine Lisicki and an Australian Open quarter-final loss to Sloane Stephens earlier this season had her judging this a poor campaign. \"I definitely feel a lot better with a second Grand Slam under my belt this year,\" Williams said. \"I felt almost disappointed with my year, to be honest. I wasn\'t happy with my performances in the other two Slams.\" And this is a season where she has won nine titles, a one-season personal best, and more than $9 million, the best one-year haul by any woman, while going 67-4. Until the final, Williams had lost only 16 games in six US Open matches. Adding Mouratoglou as a \"consultant\" alongside her original coach, father Richard Williams, and her sisters, including seven-time Grand Slam champion Venus, has given Williams a formidable entourage and a confidence boost. \"In general, they all really love me,\" Williams said. \"They all want to see me do great. That\'s everybody: my mom, my sisters, coach, everyone. And they get just as nervous I think as I do. \"They believe in me even more than I do. That\'s a great feeling.\" From : AFP