After an extraordinary run, Djokovic has been merely ordinary, by his high standards. Over a seven-year stretch from Wimbledon in 2009 through the French Open last year, he played all 28 majors and reached 28 quarterfinals, 24 semis and 18 finals, winning 11. In a sport increasingly dominated by veterans, Djokovic was getting better as he aged, netting seven finals and six titles from his last eight majors of the stretch. Since then, though, he has a second-round loss, a final loss and a third-round loss. That kind of run used to be respectable even for the world’s best players: Sampras had a worse three-major stretch when he was No. 1 in 1997-98. But more recently Djokovic, Federer and Nadal set a much higher standard of consistency. Now that all three are struggling, Andy Murray has capitalized, winning 29 of his last 30 matches to take a commanding lead in the rankings over No. 2 Djokovic.Djokovic is far from finished. Some of his struggles could be chalked up to bad luck: All three of his recent Grand Slam losses were close, and came after a stretch in which he’d won all his close calls. He’s healthy and sounded motivated in Melbourne after having discussed his quest to find emotional fulfillment on the court last fall. Even during his slump, he has won six of nine matches against fellow top 10 players, including a defeat of Murray two weeks ago. He was favored by experts and Elo ratings to win the Australian Open, and barring injury he’ll be one of the favorites at each of the year’s remaining three majors.But time is not on his side. With each upset loss, Djokovic becomes a little less likely to catch up to his rivals for the sport’s most distinguished record. Share on Facebook Seven months ago, it was hard to imagine Novak Djokovic losing a Grand Slam match: He’d won his last 28, and 53 of his last 55. And 24 hours ago, it was hard to imagine him losing an Australian Open match: He’d won his last 15, and 40 of his last 41. But on Thursday in Melbourne, Djokovic crashed out in the second round to Denis Istomin, 7-6(8) 5-7 2-6 7-6(5) 6-4. Djokovic will be 30 by the time the next major starts (the French Open begins May 28), and he’ll still be stuck on 12 career major titles. His pursuit of Roger Federer’s record 17 titles has stalled out around the same age that slowed Federer and the other two guys Djokovic is chasing: Rafael Nadal and Pete Sampras.