SATISFACTION is the enemy of the top-class athlete but Andy Murray could last night indulge in the smallest portion of contentment.

This will pass quickly, of course, but his march to the Barclays ATP World Tour finals in London later this month has been achieved with a spring in his step and with a a strength of will that has echoes of the glory days.

The brisk termination of Grigor Dimitrov in Paris last night was the physical manifestation of an approach that can be summarised, Schwarzenegger-style, in the phrase: "I'll be back."

It has been a long, arduous year for Murray as he has attempted to return from back surgery. The O2 in London for the tour finals will be an appropriate stage to take a bow for his spectacular end to the season.

It was fitting, too, that Dimitrov served as the welcome mat to the season-ending finale. On July 2, Murray sat in a backroom at Wimbledon, drained by a straight sets defeat by the Bulgarian and vowed to work harder, to fight to retain his place at the top. There were doubts among those who listened.

But did Murray have faith that he could stay ahead of the Dimitrovs, the Kei Nishikoris, the Stan Wawrinkas and catch the Big Three? Did part of him believe that his back surgery ensured that he would never be quite the same? Was there the nagging, but dispiriting concern that he had climbed the mountain and did not have the strength for the assault on another summit?

His friend and confidant, Sir Alex Ferguson, maintains the most difficult task for the elite is to repeat success immediately. Murray, at first hampered by the back injury and then constrained by a recovery programme, had to achieve this under difficult circumstances.

He has now lost just two matches out of 22, has taken three titles and has won 11 successive contests. He has, almost incidentally, pocketed more than $3m this season but will be more rewarded by the sense of well-being that a restored game offers.

Jamie Baker, his friend and Davis Cup team-mate believes that Murray, eighth in the world, will now go on to regain his seat at the very top table. Baker, who retired in 2013 and is now in banking, is not being glib or facile in that assessment, believing Murray has yet again used adversity to find an impetus back to both form and fitness.

"It is impossible to put yourself in his shoes," he says. "But he must have been thinking after he won Wimbledon: 'What happens now?' He had achieved his lifelong ambition and even without the surgery there would have to have been a reflection on what had happened and what could happen next. Anything he does can not match-winning Wimbledon for the first time."

The attempt to reach tour finals, though, has provided the spark that has reignited Murray's game, says Baker. "It is very, very difficult to maintain motivation at the highest level. I cannot imagine what it is like to achieve something that great such as winning Wimbledon and then having to continue to put all that work in every single day"

Baker has been on training blocks with his friend and knows precisely the demands that are made of Murray. "You just cannot go through the motions at that level. It does not work like that. The intensity just does not lessen."

Baker says the first signs of a Murray recovery came when the Wimbledon and US open champion talked about moving well. The second came when Murray won tough, long matches against the likes of David Ferrer and Tommy Robredo.

'Andy obviously places great emphasis on the way he feels on court. If he loses, if he has bad results, if he is off the pace, the first thing he will talk about his movement. Conversely, if he is playing well his first remarks will be about how well he is moving.

"The other factor is that he would need absolute, concrete evidence that he was back to full strength. There is only one way to have this and that is to endure the sort of physical matches that he had against Robredo the other day."

Murray saved five match points against Robredo in the final of the Valencia Open on Sunday when he fought back to win 3-6, 7-6 (7), 7-6 (8). At three hours and 20 minutes, it was the longest final of the year on the ATP World Tour..

"Andy would have been saying to himself after that: 'I am back'. He would have had his doubts before surgery and he would have had his concerns after it. That is natural. But what is different with Andy is that he has to take his body to extremes."

Asked if the wider world underestimated the impact on Murray of back surgery. Baker replies: "It is not a matter of underestimating it, it is a matter of understanding. Unless you have been an athlete it is hard to understand just what is required physically. Take the Robredo match the other day. This was about going to the very limit. This was about pushing and pushing your body until you think there is no more."

Baker, too, was frank about the surgery. "We can sum it all up in clinical terms but someone has taken a knife and stuck it into his back. There is trauma in that and the body has has to adjust to that."

There has been an adjustment too in Murray's thinking. After the US Open, he seemed resigned to missing out on the tour finals or, at least, that they were not a priority.

However, the O2 became a target he could focus on and the route to London also was signposted by a significant fringe benefit.

"One of the things he has been thinking about is the draw in big tournaments," says Baker. "His draws have been pretty horrendous in some tournaments. He is smart about tennis. He knows he can win grand slams but he knows, too, when you are ranked 8-10 it becomes a very much harder task because it is less likely that somebody puts one of the big guns out before you play them. And you may have to beat four top players to win a grand slam."

London now calls before Murray heads to Miami for a training block and the major season starts with the Australian Open in January.

'He is two tournaments away from being back where he wants to be," says Baker. "My prediction is that by the end of February he will be in the top four."