Milos Raonic of Canada returns a shot during a men's singles quarterfinal match of ATP Mercedes Cup tennis tournament between Marton Fucsovics of Hungary and Milos Raonic of Canada in Stuttgart, Germany, on June 14, 2019. Milos Raonic won 2-0. (Xinhua/Philippe Ruiz)

Milos Raonic of Canada returns a shot during a men's singles quarterfinal match of ATP Mercedes Cup tennis tournament between Marton Fucsovics of Hungary and Milos Raonic of Canada in Stuttgart, Germany, on June 14, 2019. Milos Raonic won 2-0. (Xinhua/Philippe Ruiz)

Marton Fucsovics of Hungary serves during a men's singles quarterfinal match of ATP Mercedes Cup tennis tournament between Marton Fucsovics of Hungary and Milos Raonic of Canada in Stuttgart, Germany, on June 14, 2019. Milos Raonic won 2-0. (Xinhua/Philippe Ruiz)

Milos Raonic of Canada returns a shot during a men's singles quarterfinal match of ATP Mercedes Cup tennis tournament between Marton Fucsovics of Hungary and Milos Raonic of Canada in Stuttgart, Germany, on June 14, 2019. Milos Raonic won 2-0. (Xinhua/Philippe Ruiz)