NEW YORK (AP) — Playing mostly mistake-free tennis, top-seeded Novak Djokovic reached the quarterfinals at the U.S. Open for the eighth year in a row — and 22nd consecutive Grand Slam tournament overall. Djokovic, the 2011 champion at Flushing Meadows, made only 19 unforced errors, saved both break points he faced, and breezed past 22nd-seeded Philipp Kohlschreiber of Germany 6-1, 7-5, 6-4 Monday. The last time Djokovic was eliminated before the quarterfinals at a major was a third-round loss to Kohlschreiber at the 2009 French Open. Next up for the Serb, who reached the U.S.