Wimbledon: Novak Djokovic blames stomach issues for sluggish first-round performance

Djokovic was in dominant form for much of the second set and at one point in the tie-break he had won 97 per-cent of the points when he landed his first serve, winning 32 out of 33 points.

Yet he spurned 11 break points and including four set points, before losing the tie-break when he was also in a commanding position in that.

Djokovic found his form again to win the match with some ease, but he confessed he was concerned about the issue that threatened to undermine his Wimbledon challenge.

"It went from my absolute best feeling, best game in the first set, many break chances to break in the second, to my absolute worst feeling in a long time," said Djokovic.

"I had issues with the stomach. My energy completely dropped. I was just, yeah, trying to survive on the court for quite some time.

"Then after a while the energy came back, and I could go back playing from the baseline the way I played in the first set."

Djokovic's booming serve was an impressive element of his opening to the match and while he was clearly concerned by his sudden dip in energy in the second set, he suggested his ability at the net is a facet of his game that could be vital to his hopes of winning a record-equalling eighth Wimbledon title.

"If you go back to the very early years of my professional career, I was coming into the net quite a bit actually," he said, in another of his forthright and detailed press conferences.

"I had that kind of tennis game style where I would take a short ball and just come in on any surface really, particularly quicker ones.

"Then I kind of backed up a bit, and I wasn't really keen on getting to the net. I was just playing a little bit more passive in the years to come. It really does depend.

"I think in the important points, sometimes you try to go for it, and then you really try to take the ball early and come to the net and maybe close the angles to your opponent. Depends who you play really.

"But I always try to have all the shots in my arsenal, so to say. I always try to be a very versatile player who can adapt to any conditions, any surface, or any opponent for that matter.

"I think it's important to have a very complete game nowadays. We don't have that many serve and volleyers because the return game of players has improved so much. The balls have gotten slower and bigger. It's not easy to finish the points at the net.

"Nevertheless, on this surface, it does really help if you have confidence to come in and know how to play, how to position yourself. I wouldn't say I'm a very natural volleyer, but I think I have - you're right - maybe in the last five, six, seven years have improved that quite a bit and tried to work on that serve and volley, particularly on quicker surfaces."

The biggest concern for Djokovic heading into his second-round match against Britain's Dan Evans might not be the opponent across the net, but the illness that may be a factor in what comes next as he looks to win a record-breaking 25th Grand Slam title.

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