Thursday 17 July 2014 04.43 EDT Last modified on Monday 4 April 2016 11.02 EDT. Serena Williams’s coach, Patrick Mouratoglou, has revealed the world No1 is in a “difficult period” but confirmed he would be staying on in his role. Williams has struggled all season, failing to progress beyond the fourth round of the three majors so far and at Wimbledon, her form came under further scrutiny.