NEW YORK (AP) — Novak Djokovic has started his bid to make history at the U.S. Open with a four-set victory over Danish teenager Holger Vitus Nodskov Rune. The top-seeded Djokovic is trying to complete the first calendar-year Grand Slam in men’s tennis since 1969 and collect a record-breaking 21st major singles championship. Djokovic was not perfect but he didn’t need to be. He won 6-1, 6-7 (5), 6-2, 6-1 to get to the second round. Rune is an 18-year-old who is ranked 145th and qualified at Flushing Meadows. Rune started having problems with cramps in the third set.