Stan Wawrinka reacts during Sunday's French Opne final against Rafael Nadal. Photo: Reuters / Christian Hartmann

LAUSANNE, Switzerland - Stan Wawrinka has called in coaching reinforcements for the pre-Wimbledon season with the Swiss hiring American Paul Annacone to help guide him on the grass.

The 32-year-old French Open finalist has a longstanding and highly successful coaching relationship with Magnus Norman, a former Roland Garros champion. Annacone who coached Roger Federer from 2010 to 2013 will bring his specific grass expertise to the team.

"I have added Paul Annacone to our existing coaching staff to help during the grass-court season over the next four weeks," Wawrinka said in a statement. 

"Paul's experience speaks for itself having worked with some of the greatest players of all time. His knowledge can only better our understanding of the grass. It's a real privilege and honour to add such a coach to our corner."

Annacone also coached former world number one Pete Sampras from 1995-2001 and again briefly the next year.

Annacone, a television commentator, will work alongside Swede Norman, who has been responsible for the renaissance of three-time grand slam winner Wawrinka,

Wawrinka's new lineup will get its first test next week at the Queen's club event in west London where Wawrinka reached the semi-finals three years ago.