Andy Murray joined Stan Wawrinka and Marin Cilic on the Coupe Rogers sidelines on Thursday when he announced that he would not play Montreal next week.
The Scot, who has won the tournament three times—in 2009, 2010 and 2015—will miss the event for a second consecutive year as he continues to recover from a hip injury.
The Masters 1000 event begins on Monday.
With Murray out, Rafael Nadal has a golden opportunity to retake the top spot in the rankings for the first time since June 2014, shortly after he won his ninth French Open.