The saying suggests you cannot teach an old dog new tricks. But ask experts in the canine business and they will insist you can with a top-class trainer.
That is what Tottenham have and if Mauricio Pochettino can turn Moussa Sissoko into a top performer it will be one of his biggest successes so far.
It has been a poor start to the season for Spurs at Wembley, but the away victory at Everton underlined their quality – and Sissoko’s performance was a surprising bonus.
There are a string of players Pochettino has straightened out, sanded down and moulded in his image, but most of them have been young, or youngish.
Youth graduates like Harry Kane and Harry Winks are plain to see, while Kyle Walker and Danny Rose are to name just two more. But they were in their early 20s when the Argentinian arrived.
At 27 in 2014, Mousa Dembele was the oldest player that Pochettino has developed but his quality had been evident before. Sissoko is 28, yet far from the finished article.
But if his performances so far this season are anything to go by, especially at Everton, the ongoing sculpting job on Sissoko is looking good.
The player has said he is benefiting from full pre-season with the squad and he does look fitter. But Pochettino does much of his tactical work in the summer and Sissoko appears to fit the system better.
Much of his influence at Goodison was arguably down to playing in a more natural position, as he operated in central areas like a traditional number eight – exactly where he thrived for France at the 2016 European Championships.
Spurs signed him weeks after that tournament, but only having searched for a right winger after failing to land Wilfried Zaha. And it has been impossible to see that kind of player in Sissoko, who struggled repeatedly in that position last term.
He is not a natural at beating players with pace or skill, and his crossing has been suspect. But he reads the game superbly, passes well, and barraging past opponents he can do.
Pochettino wanted to sign a new number eight in the summer and Everton’s Ross Barkley was the target, but his injury meant Spurs have opted to wait until the next transfer window to move.
In the meantime, Sissoko has the chance to become that player himself and make his boss think twice about his January plans.
There is still much chiselling still to be done on a man who, superficially at least, looks like he has been carved from granite. Sissoko’s first touch is, at times, like bouncing it off a dry stone wall.
But there was a move at the weekend, in which he made a deft pass before arriving late in the box and shot at Jordan Pickford, that highlighted what he can do.
He could yet be the answer in that position – and the kind of £30m signing Tottenham wanted.