BASEL, Switzerland — Three-time Grand Slam champion Stan Wawrinka has ended his season after withdrawing from the Swiss Indoors with a back injury.
Wawrinka says there is "disappointment and sadness" in taking a decision for his long-term plans.
The 33-year-old Swiss, who was due to play Wednesday against Adrian Mannarino, is now ranked 68th after battling knee injuries for more than a year.
Third-seeded Marin Cilic moved into the second round by beating Denis Shapovalov of Richmond Hill, Ont., 6-4, 6-2.
Cilic can confirm his place in next month's ATP Finals in London by repeating his 2016 title in Basel.
Top-seeded Roger Federer is seeking a ninth career title at his hometown tournament.
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