Juan Martin del Potro announced Wednesday that he is pulling out of the Rogers Cup in Toronto because of a left wrist injury.
Del Potro wrote on Twitter that his wrist "needs some days of rest."
Del Potro, 29, seeded third in the tournament, was scheduled to play Robin Haase on Wednesday.
The 2009 US Open champion, who is ranked fourth in the ATP rankings, is 35-9 this season and has won two titles.