Arsenal signing Alexandre Lacazette is one step forward, but losing Alexis Sanchez would be two steps back

The Frenchman promises to be a fine addition, but if Wenger repeats his trick of 2012 then Arsenal promise to regress even further

The joy of Lacazette's arrival could be short-lived should Alexis Sanchez be sold this summer (Getty)

Arsene Wenger was trying and failing to persuade his best player to sign a new deal at Arsenal. He only had one year left and Wenger was desperately reluctant to sell him to a rival. But he knew that he might have to, so he signed a promising French striker from Ligue 1 as a potential replacement.

For 2017, read 2012. The same situation Wenger is in now, trying to cling onto Alexis Sanchez, and signing Alexandre Lacazette from Lyon, he went through five years ago. Then, with Robin van Persie threatening to run down the last year of his deal, Wenger spent £10million on a relatively unknown 25-year-old who had just fired Montpellier to the French title, Olivier Giroud.

By any fair measure, Giroud has been an excellent value at that price. He has given them five good seasons and scored 98 first team goals. £100,000 per goal is certainly not a bad return for the top end of the Premier League. It is no surprise that even now, as Giroud approaches his 31st birthday, he has some pretty serious teams in England and abroad trying to sign him. He has served Arsenal well.

And yet we all know that Arsenal replacing Van Persie with Giroud was a serious downgrade. Van Persie was at that moment the best centre-forward in the country. In the 2011-12 season he scored 30 Premier League goals, the most by any Arsenal striker since Thierry Henry scored 30 in the Invincibles season. 2011-12 was not exactly vintage Arsenal , certainly not compared to the Henry era, but they did at least finish third. And then that summer they took one step forward and two steps back.

Arsenal scored 74 Premier League goals in 2011-12 and it was only in the season just gone that they finally beat that total for the first time since Van Persie left. Wenger predicted when he sold Van Persie that his goals would be equally distributed among his team-mates but it never quite worked out like that.

Only now are Arsenal back to that goal-scoring level, because only now do they have a world class striker again. The use of Sanchez as a centre-forward gave Arsenal an extra edge last season. They are a completely different proposition with and without him which is why he, unlike Mesut Ozil, is unquestionably worth breaking the bank for.

Which means that if Arsenal do sell Sanchez this summer then they will be facing the same dramatic downturn they did five years ago, no matter how good Lacazette might be. That is why Wenger is publicly flirting with the possibility of keeping Sanchez, even if it means missing out on a £50million fee that Manchester City would be more than happy to give them. At one press conference in March he even said that the remaining £8m in ‘book value’ that Sanchez had in the Arsenal accounts meant that selling him would not be quite as lucrative as it might look.

The problem for Wenger is that he made the same pledges about Van Persie five years ago as he is making about Sanchez now. Why would anyone believe that he is going to dig in, say no to the player, and say no to the money, when he made the same promises and then caved in 2012?

So if Sanchez does go then Arsenal are going to have to face the prospect of a long search to replace him. Not just his goals, but his energy, inventiveness, leadership and all the other intangibles you only get from a player that good. The only way to replace world-class, unfortunately, is with world-class. And while Lacazette is a very effective player at Ligue 1 level he could not beat Giroud to place in the France squad for Euro 2016.

For Arsenal to get out of this summer, if they do lose Sanchez, without their gradual gains of recent years evaporating, then their other attacking players will have to do very well indeed. Or else they will find themselves back at the foot of the mountain, with another long climb ahead of them.