Former world No. 1 John Mcenroe has weighed in on the 2017 season of Andy Murray and Novak Djokovic. This campaign turned out to be a huge disappointment for Scot Murray and Serbia's Djokovic. It has been a challenging season both on and off the court for the two tennis superstars.

"It is difficult to say because each person is different. I'm not close enough to them to know exactly what happens, but it seems that Murray's is physical and Djokovic's is mental. What's also true is that sometimes an injury affects you on the mental level and vice versa," former seven-time Grand Slam champion McEnroe told Marca.

Murray is on the brink of calling it a season.

Murray, 30, hasn't played since Wimbledon. American Sam Querrey edged the Scot in the Wimbledon quarter-finals this past July. Murray was failed by his hip as he was clearly bothered and in pain during the match.

Since the championships, Murray has been giving his best efforts to recover from a hip injury. Murray hoped to make a comeback at the US Open -- but he didn't recover in time. The three-time Grand Slam champion later revealed on his social media accounts that he is out of this week's China Open in Beijing and the upcoming Shanghai Masters. He also noted that he is not likely to play at the Vienna Open and Paris Masters -- which would automatically rule him out for the year.

Unfortunately, Murray hasn't been troubled only by his hip this season. The Scot recovered from shingles and an elbow injury earlier this year.

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Murray has been struggling to find his form and consistency the whole season. The 30-year-old's year includes no Grand Slam or Masters 1000 trophies. His only title of the year was achieved in Dubai at the beginning of the season.

Djokovic taking his time

On the other side, Djokovic has already called it a year. Djokovic was forced to retire his Wimbledon quarter-final clash to Czech Tomas Berdych. Shortly after Wimbledon, the Serb announced that he is taking a break to heal an elbow injury.

Like Murray, Djokovic has also failed to be a strong force at the biggest events. Djokovic will have finished the year without any Grand Slam or Masters 1000 titles captured this season. However, the Serb came close to winning the Rome Masters, but he was stopped in the final by rising Alexander Zverev. Djokovic won the Doha event in the opening week of the season and also ended champion at Eastbourne just a week before Wimbledon.

Murray and Djokovic not ready to quit

Murray and Djokovic will be eager to bounce back in 2018. After a couple of years of playing at a high level, both simply couldn't be the same dominant players this year. The two are hoping to benefit from their respective lengthy breaks. It would be hard not to see Murray and Djokovic recover physically and mentally and compete for the biggest titles going forward.