John McEnroe will join Milos Raonic's coaching team ahead of the upcoming grass-court season.
World number nine Raonic has only ever won ATP titles on hard courts, but reached the semi-finals of Wimbledon in 2014.
McEnroe had been linked with Andy Murray as the world number two continues his search for a new coach after parting with Amelie Mauresmo.
But the American, a former world number one and seven-time grand slam winner, believes Raonic has the potential to win majors and hopes to help bring that out of him.
"Milos Raonic can win majors. He's one of five or six guys that can win Wimbledon. I'm excited to be part of his team," McEnroe said on Eurosport.
"Milos has a great team with Ricardo Piatti and Carlos Moya. I'm going to be a consultant on the grass. I'm excited."
The Canadian – who is through to the fourth round of the French Open – is scheduled to play at Queen's Club Championships before Wimbledon begins on June 27.