Novak Djokovic sought assistance from a trainer for some trouble breathing Friday night, and went back-and-forth with one particularly loud spectator, but when the ball was in play at the Australian Open against Tomas Machac, all went quite smoothly for the 24-time Grand Slam champion. Djokovic, a 10-time title winner at Melbourne Park, moved into the fourth round with his most confident performance of the week, a 6-1, 6-4, 6-4 victory over the 26th-seeded Machac — who actually won their most recent previous encounter, last season. It all lasted less than 2 1/2 hours, and Djokovic was broken only once and converted 5 of 15 chances on Machac’s serve.
