“That is the danger in the modern game and the problem I find in clubs,” said McClaren, the former England manager and Alex Ferguson’s assistant when United won the treble in 1999. “Wage parity is very important to players. Yes, they find out - at all levels - and if someone is paid a lot higher than others that can cause a problem.

“In the short term I don’t see a problem, but in the long term for United they will have to solve that problem. If he (Sanchez) is on the wages that is being bandied about then other players will know that when their contracts come up or they are in demand from other clubs.

“The others will be looking at renegotiation next season or the season after and getting to that (wage) level if they think they are at that level.”

But McClaren believes United have struck a major blow by landing Sanchez, who has scored 80 goals in 166 appearances at Arsenal.

“Any manager worth his salt would love to have Sanchez in their team,” McClaren said.

“Sanchez coming in for the second half of the season at United is a huge boost to them. He has got that experience and toughness, he wins games and he is a leader.

“It will lift the level of the whole club.”

Both Sanchez and the player going the other way, Henrikh Mkhitaryan, were undergoing medicals yesterday. Sanchez flew to Manchester on a private jet – posting footage on Instagram - and was later photographed being driven to Manchester United’s training ground at Carrington.

Former Arsenal midfielder Emmanuel Petit says that, in purely sporting terms, losing Alexis Sanchez to United is the result of “a bad decision” by Arsenal.

And the French world-cup winner fears Henrikh Mkhitaryan may not have the winning mentality to radically alter Arsenal’s fortunes and may prove too similar to new teammate Mesut Ozil.

Petit wrote on his blog for Paddy Power: “It’s a good deal, but it could have been a great deal if it had been done in the previous window, and may have allowed them to bring in reinforcements then. Instead, they ended up with an off-key Sanchez for six months, so in purely sporting terms, it was a bad decision.

“Alexis will be an excellent player for Manchester United. They’ve got a top-quality footballer, with the skills and mentality to survive at the elite level. He will be extremely motivated to perform for them, considering he’ll get the money he wants and will be playing for one of the biggest clubs in the world in the Champions League. He’s exactly the type of player United need, and he could be the missing link for them.”

“As for Mkhitaryan, since he signed for United he hasn’t been involved enough. I’m not sure he has a winning mentality, and sometimes he reminds me of Ozil: you really have to push him to show his character and put him under pressure to display his best qualities. There’s no doubt he has great skill, but I’m not sure he’s the kind of player that Arsenal need – they should be focused on other positions.”

Petit accepts the Premier League landscape has changed since his heyday at Arsenal under Wenger, but warns the Gunners will need to pay higher wages to have a chance of returning to the summit of English football.

“Arsenal are struggling to bring in top-quality players, and also to keep the ones they have. It has been like this for a long time. They must be more competitive on the market, both when buying and selling.

“Times have changed since I left Arsenal, but I’m pretty sure Arsène is still heavily involved when it comes to the transfer market, but I wonder about the quality of players they have been signing. There has been a lot of speculation about the likes of Aubameyang and Malcom – but with the money Arsenal have, they should be aiming higher.

“Because they are not competitive on the pitch at the moment, they need to be more competitive with wages: if you can’t guarantee trophies or at least compete to win them, then you must offer players more in order to come to the club. That’s just the way it works.”