(CNN) -- Roger Federer has decided to employ the services of top coach Paul Annacone as he attempts to rediscover his form ahead of the final grand slam of the season, the U.S. Open, in September.
Federer has dropped to number three in the world rankings behind Rafael Nadal and Novak Djokovic, following his shock defeat to Tomas Berdych in the Wimbledon quarterfinals last month, and now stands at his lowest position since November 2003.
As a result, the Swiss has turned to American Annacone -- who has previously coached both Pete Sampras and Tim Henman.
Speaking on his official website, Federer revealed: "I've been looking to add someone to my team and I've decided to spend some days with Paul Annacone.
"As Paul winds down his responsibilities working for the Lawn Tennis Association, we will explore our relationship through this test period.
"Paul will work alongside my existing team and I am excited to learn from his experiences," he added.
Annacone will leave his position as head coach of men's tennis in Great Britain in November after handing in his notice earlier in the year.
Federer has worked with Australian coaches Peter Carter and Tony Roche in the past, but has had no permanent coach since splitting from Roche in 2007 -- although he has been working with Swiss Davis Cup captain Severin Luthi.
Meanwhile, world No. 4 Andy Murray has sacked one of his coaches, Miles Maclagan, having worked with his fellow Scotsman since late 2007.
The 23-year-old, whose first tournament since losing in the semifinals at Wimbledon last month is this week's Farmers Classic in Los Angeles, will keep working with Spanish coach Alex Corretja.