World No. 1 Novak Djokovic needs to step up his game offensively as he enters the final Grand Slam tournament of the year at the U.S. Open in Flushing Meadows on Monday.

The 27-year-old Djokovic will play Argentinean Diego Schwartzmann in the main event at 7:00 p.m. on Monday at the Arthur Ashe Stadium.

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Djokovic hasn't been playing good tennis after his win at Roland Garros. He exited early in the third-round in both the Rogers Cup and recently concluded Western and Southern Open.

He has been ousted in Toronto by eventual winner Jo-Wilfried Tsonga and Tommy Robredo in Cincinnati.

"Maybe I think about my defense too much," Djokovic said in a USA Today interview. "I have to get more in the offensive mode."

If all things go well in the first four rounds of the U.S. Open, Djokovic may be looking at a possible Tsonga or with British No. 1 Andy Murray matchup in the quarter-finals.

That alone is a major hurdle in Djokovic's second U.S. Open title quest. If he goes onto the semi-finals, he is most likely to face Swiss Stan Wawrinka or Canadian Milos Raonic which are both powerhouse servers.

Defending U.S. Open champion Rafael Nadal won't be able to compete in the tournament due to a wrist injury. Replacing him as second seed is 17-time Grand Slam champion Roger Federer.

The 33-year-old Federer's last Grand Slam title was at Wimbledon in 2012 and last won the U.S. Open in 2008 however, he is playing well as of late winning the crown in Cincinnati and placing second to Canada Open winner Tsonga.

Djokovic last faced Federer in the recent Wimbledon finals in a classic five-setter and if all things go into place, they might face against each other again in the U.S. Open finals.

TagsNovak Djokovic, Roger Federer, rafael nadal, Milos Raonic, Stan Wawrinka, Jo-Wilfried Tsonga