Juan Martin del Potro has withdrawn from the Rogers Cup due to another wrist injury.
Del Potro was given a first-round bye in Toronto, but pulled out ahead of his second-round match with Robin Haase on Wednesday.
The 2009 US Open champion underwent four wrist operations and considered retiring before returning in 2016.
Del Potro has worked his way back up the rankings and reached the semi-finals at Flushing Meadows last year before doing the same at the French Open in June, a run he followed by progressing to the quarter-finals at Wimbledon last month.
He was beaten by Rafael Nadal in each of those tournaments but Del Potro's resurgence has seen him rise to fourth in the rankings.
The powerful Argentine indicated that his latest setback is not serious with under three weeks to go before the final grand slam of the year in New York.
He tweeted: "Sorry to my fans but I have to pull out of the tournament since my left wrist needs some days of rest. Hope to see you next year in Montreal!"