On the eve of the US Open, the British number one and world number three Andy Murray is being widely discussed as one of the favourites for the title, an important summer win over a big rival doing much to convince doubters that he has what it takes to beat the best in the biggest matches.

The important summer win I mention is of course his 6-4 4-6 6-3 win over Novak Djokovic in the Rogers Cup final, his first over the world number one since the 2013  Wimbledon title match. 

But, that opening sentence could just as truthfully been written this time three years ago, not long after Murray's first win over Roger Federer in a best of five set match. The Scot, as we all know, did indeed go on to win the title that year, 2012, and it seemed that his defeat of Federer in the Olympic final did much for his own belief in his ability to beat the best over the longer, tougher format of five-set tennis.

And yet, here we are, three years on, with the same questions circling the two-time major champion at the same stage this year.

Murray struggled after surgery

It's perhaps not a surprise that we are back here, given Murray's back surgery almost two years ago, and his trials throughout 2014 as he recovered from it. Although Murray struggled at times against lower ranked opposition last year, there were also several occasions where he would look good in overcoming lesser opponents, only to fail to come through tight matches with his fellow big four members, or to be subjected to a thrashing, as he was when winning just one game off Federer in his final match of 2014.

Of course, against such illustrious opposition, there's hardly anything wrong with being edged out in tight matches, but it was his overall record - the big three that was the cause for concern - 0-9 in 2014.

Murray permanently reverting to the player who is outstanding in defeating his early round opponents, before predictably falling to a fellow big name was a genuine and major cause for concern, and this continued into 2015, a good start against Djokovic in the Australian Open final ending with the Serbian winning 12 of the last 13 games - exactly what had happened against Federer at the O2 arena a few weeks earlier.

But things finally started to turn around in the spring, the British number one perhaps getting back to his best mentally, where he was already as impressive as ever physically. A win over Rafael Nadal in the Madrid Masters final was not just his first clay Masters title, but also his first win over Nadal on the surface, and his first win over a fellow big four member since beating Djokovic to the Wimbledon title in July 2013.

Sure, Nadal has been having his own, just as troubling, difficulties, but the win must still have been both a relief and a huge psychological boost as the tour moved into its busiest stretch of the season.

Murray's continued good form following his Madrid title has seen him put together what is surely his most consistent season to date, but he still had to wait until August to snap an 8-match losing streak against Djokovic, and he remains winless against Federer since January 2013.

And of course, he remains without a best of five set win against any of the big three since his surgery.

Scot facing familiar challenge

Will the 2012 champion be able to get over that hump in New York this fortnight, just as he did in three years ago? While it's always tough to predict that a player will beat an opponent they've frequently lost to - Murray is a combined 1-13 - Djokovic and Federer since winning Wimbledon - you'd have to say that having overcome this particular challenge before is likely to work in the Scot's favour.

In 2012, it was his Olympic victory over Federer that inspired Murray to believe in his ability to win, and while his victory this month over Djokovic in Montreal was an important one, it is perhaps for slightly different reasons.

Three years ago, the British number one knew full well that he was capable of beating his fellow elite players in 3-set matches, he just seemed to lack the belief that he could do the same over five sets. Winning the gold medal proved to himself that he could, and a first major title soon followed.

This time around, Murray needed to prove to himself that he could still beat these players at all post surgery. Having now overcome Djokovic, is he ready to do so in a Grand Slam tournament again?

Final set toughness the key against Djokovic

We won't truly know until they next meet, but looking back to their match at the French Open could give us some clues. Murray had leveled the match at two sets all by winning the third and fourth sets, before losing a one-sided fifth, the score 6-1.

That sort of final set scoreline seems to suggest perhaps a lack of true conviction that he could win - that after hours of going toe-to-toe with the world number one, the finish line still seemed impossibly far away. This is where his Montreal win could help him, as it was a match where he did exactly what he had needed to in Paris: continue to play with conviction, continue to be aggressive right up until the final point.

Having now proved to himself that he can overcome the Serbian in a tight match in the final set, Murray has set himself up well to beat Djokovic in a five set match once more, to win those matches where he has been disappointing in the final set. No one is suggesting that wins will come easily, but you do feel that the Scot is finally mentally ready to do it again.

Change of tactics could help against Federer

Roger Federer is a different proposition altogether. He's been able to best Murray both times they've played this year with hyper-aggressive tennis, even half-volleying Murray's serves in Cincinnati. Such tactics have worked superbly against the naturally more defensive Murray, who has had no answer to Federer's excellent serving or his constant net-rushing.

This year at least, Murray's prblems against Federer seem to have had more to do with the tactics and playstyles than Murray's self-doubt. Murray is certainly not the first player to have been overwhelmed by Federer on top form, but perhaps it's time to try something different against the Swiss.

The world number three has excellent touch at the net, so maybe a conscious effort to attack the net much more often could help him against Federer. It would certainly be something different for Federer to deal with, and so ineffective has Murray been against the 17-time major champion, that that 'something different' could be just what Murray needs for another win.

It's worth noting, however, that a good mentality and a good gameplan are not always enough on their own to overcome any of the world's elite at their very best, including Murray himself. Even if the Scot is not triumphant this fortnight, just as in 2012 he seems to be getting closer to overcoming the final obstacles standing between him and a third Grand Slam title.