NEW YORK (AP) -- Novak Djokovic had become rattled by Tennys Sandgren and a boisterous Arthur Ashe Stadium that knocked him off his game. But his most troublesome antagonist at the U.S. Open came from within. ''The other me,'' Djokovic said with a smile, ''that my first me doesn't like.'' The alternate version of himself that Djokovic detests - when his mind, more than his skill, becomes the problem - surfaced in a puzzling third set when the 31-year-old Serb was only one point from victory but couldn't close the deal. ''You just have to accept it sometimes,'' Djokovic said. ''But that's being a human being, I guess. Not human doing.'' Whatever it was, Djokovic straightened himself and kept on a path toward a third U.S. Open championship . Djokovic wasted a match point in the third set, before going on to win 6-1, 6-3, 6-7 (2), 6-2 against Sandgren on Thursday night at the U.S. Open to reach the third round. Djokovic had a much easier victory over Sandgren, an American ranked 61st, in Wimbledon's first round this year, dropping only six games in all. The 13-time major champion seemed to be along the same path at Flushing Meadows, standing one point from victory while leading 5-4 in the third set as Sandgren served at 30-40. But Sandgren ended an 11-stroke exchange with a forehand winner, then took the tiebreaker . Sandgren, who made a surprising run to the quarterfinals at the Australian Open, noticed Djokovic's dip in the third. ''It's tough to stay really focused and clean for three full sets. It's just difficult to do,'' Sandgren said. ''If anybody can do it, he can. But he definitely blinked there for a moment.'' Djokovic, the 2011 and 2015 champion, regained the upper hand with an early break in the fourth and was on his way. But it wasn't a fan-friendly victory. Djokovic whined at Wimbledon when he was booed at times on Centre Court and he complained again at the U.S. Open about fans who turned the night session into a bit of a party. Story continues He got on the fans during his post-match interview on the court for talking during points and said he lost his concentration. ''You can't expect that 23,000 people are quiet,'' he said. ''That's the beauty of night session U.S. Open. Everybody knows that. Wimbledon is all white, it's tradition. You can't hear a sound when you play a point. Here it's different. That's why these majors are unique in their own way.'' He has reunited with coach Marian Vajda - they briefly parted ways and Djokovic had a brief dalliance with Andre Agassi - to marked improvement. Djokovic knocked off Roger Federer in August to win a title in Cincinnati and a renewed focus with Vajda has been a key factor. ''When he came back, obviously we had to analyze what has happened in the last 12 months that we were not together and try to understand the situation with my body, with my game,'' Djokovic said. Djokovic, who missed last year's Open with a sore elbow, won his 13th Grand Slam title this year at Wimbledon. To get 14, he'll have to keep his ''other me'' under wraps. --- More AP tennis coverage: https://www.apnews.com/tag/apf-Tennis<doc-sep>Novak Djokovic is in US Open second round action tonight When you subscribe we will use the information you provide to send you these newsletters. Sometimes they'll include recommendations for other related newsletters or services we offer. Our Privacy Notice explains more about how we use your data, and your rights. You can unsubscribe at any time. Sign up forfor news on the biggest players and tournaments Djokovic would have been hoping to avoid the blistering sun following a difficult first-round win against Marton Fucsovics. And his wish was granted as he was given a later start time for his tie with Sandgren. The Serbian required a visit from the cardiologist and an Extreme Heat break during his four-set victory over Fucsovics. But the former world No 1 will play his next match under the floodlights after the US Open organisers offered him some respite. Djokovic takes on Sandgren on Arthur Ashe Stadium at midnight (BST) and tennis pundit Jim Courier believes the scheduling will hand the 31-year-old a huge advantage.<doc-sep>When you subscribe we will use the information you provide to send you these newsletters. Sometimes they'll include recommendations for other related newsletters or services we offer. Our Privacy Notice explains more about how we use your data, and your rights. You can unsubscribe at any time. Sign up forfor news on the biggest players and tournaments Djokovic struggled with the severe heat during his opening victory against Marton Fucsovics and required the attention of the cardiologist midway through the tie. The overwhelming temperatures got to both players but the Serbian recovered, with the help of an Extreme Heat break, to win over four sets. US Open officials have handed Djokovic some respite during the second round as he will avoid the glaring sun when he gets underway on Arthur Ashe Stadium at midnight (BST) tonight. And when the two stars go head-to-head, Courier believes Djokovic will ease through to the third round.<doc-sep>
Novak Djokovic struggles to find his car at Cincinnati Masters Despite having a match point in the third set, Djokovic was taken to four sets though he eventually prevailed 6-1, 6-3, 6-7, 6-2. Djokovic next faces Frenchman Richard Gasquet, who defeated Laslo Djere, though he will hope for an easier match, despite appearing to be cruising against Sandgren. The Serb mentioned the crowd noise following the victory, though put a positive spin on the potential distractions. But the Wimbledon champion admitted he was upset at something, though even he wasn’t sure what it was. "Credit to Tennys for playing well, fighting, a great attitude on the court,” Djokovic said. :I thought I played very well for the first two-and-a-half sets and then I just lost it mentally, I got p****d off at something, myself, my game, I don't know. "I'm not happy with the way I lost that concentration and composure there but I managed to regroup in the fourth. “I started talking to myself, to my team, to everyone else. But it's in these kind of moments you learn lessons and hopefully I'll move on a better player." Novak Djokovic beat Tennys Sandgren in the second round of the US Open Djokovic is among the favourites to win the US Open having recently become the first player to win each of the ATP Masters titles. And pundit Greg Rusedski believes victory at Flushing Meadows would have a huge impact on Djokovic’s career. “He is the favourite here in my opinion because the court surface is a little bit slower and by beating Federer in the Cincinnati final he is full of confidence,” Rusedski said. “Djokovic doesn’t want to be in the shadows of Nadal and Federer, and from a public point of view he is at the moment. Novak Djokovic is one of the favourites for the US Open Novak Djokovic needed four sets to beat Tennys Sandgren