World No 2 Novak Djokovic has withdrawn from the ATP Toronto Masters due to fatigue, Tennis Canada said on Sunday.
The announcement comes a week after the 23-time Grand Slam champion from Serbia fell to Spain's Carlos Alcaraz in the final at Wimbledon.
His withdrawal deprives the US Open tune-up tournament that starts on 7 August of a four-time champion.
"I have always enjoyed my time in Canada, but after speaking with my team, we believe this is the right decision to take," Djokovic said in a statement released by Tennis Canada.
"I would like to thank Karl Hale, the Tournament Director, for understanding this decision. I really hope I can return to Canada and Toronto in the coming years to play in front of great fans there."
Alcaraz denied Djokovic a record-equalling eighth Wimbledon title last week, handing him his first defeat on the All England Club's Centre Court in 10 years.
The Spaniard's victory also ended 36-year-old Djokovic's chance of a calendar Grand Slam after his triumphs at the Australian Open and French Open took his tally of major titles to a men's record 23.
Wimbledon quarterfinalist Christopher Eubanks will now gain automatic entry into the Toronto main draw.
The American defeated fifth-seeded Stefanos Tsitsipas and 12th-seeded Cameron Norrie en route to the last eight at Wimbledon.
Hale acknowledged that Djokovic, who won the Canadian title in 2007, 2011, 2012 and 2016, would be missed.
"Of course, we're disappointed that Novak won't be playing at the National Bank Open this year," Hale said in a statement. "He's an incredible player and one we know our fans were eager to watch at Sobeys Stadium.
"He will be missed but we still have a long list of sensational players confirmed for this year’s event, including 41 of the top 42 players in the world."