He at least finished the match relatively strongly, recovering from dropping the third set to clinch a 6-1 7-5 4-6 6-2 victory after two hours and 35 minutes.

Much stiffer tests lie ahead though, with Jo-Wilfried Tsonga his likely next opponent, and Murray knows he will not be able to afford such lapses if he is to figure in the latter stages of the tournament.

Murray, who had never played Kuznetsov before, said: “I got off to a good start, which obviously helped. I had a bit of a cushion when he started to get back into the match.

“He played some good stuff at the end of the second and all the way through the third. I’m happy I stayed solid. It was tough.

“I feel better than I did in the first match. Conditions are a little bit more pleasant. I made sure I ate properly and drank properly.”

Kuznetsov won the junior title at Wimbledon in 2009 but has taken time to make his mark in the senior game.

He beat David Ferrer in the second round at Wimbledon and knocked out Fernando Verdasco at the same stage here.

It was nowhere near as hot as it had been on Monday, with the cloud cover no doubt welcome for Murray, who again had his four-man fan club in residence.

The first set was near perfect for the eighth seed, who served well and struck the ball with real zip.

He then made the perfect start to the second set with another break, but the match was much tighter than it had earlier been and alarm bells began to ring when Murray double-faulted to be broken back in the eighth game.

Murray looked frustrated and from 0-30 in the next game he lost four points in a row and the chance to re-establish his lead immediately.

The 27-year-old has developed a bad habit this season of losing leads, but he did get the second break two games later and served it out.

Despite getting over that line, Murray had hit a slump, and it continued at the start of the third set.

Kuznetsov exploited the situation to break for a 3-1 lead and memories of Murray’s third-set calamity against Robin Haase in round one came flooding back.

At least he appeared to be physically fine this time and, after battling to stop the rot with a hold in the sixth game, he broke to love to get back on track.

However, the up-and-down form that has plagued his season was still very much in evidence and cost him dearly in the 10th game.

Having lost a break point on a net cord in the previous game, two loose shots gave Kuznetsov two set points and Murray did not even make the Russian work for it, serving a double fault.

Perhaps not surprisingly given his results, Murray appears to be lacking belief in the big moments, and he must have been furious with himself for being extended to four sets.

He headed off for a bathroom break, a tactic that had helped him so much in his final win over Novak Djokovic here in 2012.

And Murray was quickly ahead in the third set, breaking for 2-1 when Kuznetsov drilled a forehand over the baseline.

The Russian was under real pressure and, although he saved two break points in the fifth game, one with a brilliant drop volley, he then threw in successive double faults to hand Murray what was to prove a match-winning advantage.

Still it was not entirely straightforward as Murray immediately surrendered one of the breaks, but he got it back quickly and took his first match point with a reaction volley.