Novak Djokovic needed a bit of time to assert himself Wednesday at the Paris Olympics before taking control with a five-game run for a 7-5, 6-3 victory over Dominik Koepfer of Germany, reaching the Summer Games singles quarterfinals for the fourth time.

A gold medal is pretty much the only accomplishment of significance missing from the resume of Djokovic, a 37-year-old from Serbia who has won a record 24 Grand Slam titles and spent more weeks at No. 1 than anyone in the history of the computerized tennis rankings.