NEW YORK -- Amid all the hype surrounding Serena Williams' quest for the Grand Slam, it may be easy to overlook the year that Novak Djokovic is having.

Having already won the Australian Open and Wimbledon, the No. 1 men's player in the world could win his third major title of the year at the US Open and the 10th of his still ascendant career.

The 28-year-old Serb is 61-5 in 2015 and is more than 5,000 points ahead of No. 2 Roger Federer in the ATP rankings.

"He's arguably top five, top six all-time greats right now, approaching guys that you would've thought had a place reserved for themselves," seven-time Grand Slam winner John McEnroe said on ESPN. "If he can keep this level up for the next couple years and he doesn't get injured, you would expect...that he could get three, four, five more majors for sure."

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Still, for all his success, Djokovic hasn't done as well in Flushing Meadows as he would have liked.

The Joker is 1-4 in US Open finals (his lone title coming in 2011), and fell in the semifinals a year ago to runner-up Kei Nishikori.

Next up for Djokovic is a semifinal matchup against defending champion Marin Cilic, the man who beat Nishikori in last year's final.

The men's semifinals are set for Friday, with the final on Sunday.

The good news for Djokovic is that he is 13-0 all-time against the Croatian.

Still, Djokovic expects Cilic -- who took out Frenchman Jo-Wilfried Tsonga in a five-set quarterfinal on Tuesday -- to enter with high confidence.

"Well, I would think so because of the fact that he won his first Grand Slam title last year in New York," Djokovic said. "He hasn't lost a match, you know, 12, 13 matches in a row, so I'm sure that he feels confident."

The 6-foot-6 Cilic banged out 29 aces in his victory over Tsonga, his fastest serve hitting 129 mph.

"He has a big serve," Djokovic said. "So the serve gets him out of trouble. I know him very well. I have played with him many, many times. We are great friends. Great guy. I know what to do, and I'm opening I can execute the game plan obviously and play my best."

Cilic, meantime, has flown under the radar despite being the defending champ because most of the focus on the men's side has been on the Big Four of Djokovic, Roger Federer, Andy Murray and Rafael Nadal.

But while Murray and Nadal are already out of the tournament, Cilic is two victories from a repeat performance.

"I haven't beaten [Djokovic] ever in my career," Cilic said. "I had close matches last few years, but I haven't found the right formula to be able to win a match.

"We will see. [I'm] trying to approach every match as a new one. You know, of course when you look at the statistic that he won that many matches against me, it doesn't go in my favor, absolutely. But when you're coming to the match it's always going from zero, so it's a new match. It's different stage, and I'm feeling good here on the court."

Follow Adam Zagoria on Twitter @AdamZagoria for updates throughout the U.S. Open.