Alexis Sanchez struggled to justify his astronomical wages at first, but has rediscovered his form in recent weeks for Manchester United. Photo: Carl Recine/Reuters

Jose Mourinho says Manchester United were right to fight so hard to sign Alexis Sanchez as the Chile star prepares to face his old club Arsenal at Old Trafford on Sunday.

United gazumped Manchester City to land Sanchez in the January transfer window by making him the Premier League’s highest-paid player on £600 000 per week.

The 29-year-old struggled to justify his astronomical wages at first, but has rediscovered his form in recent weeks and is now more settled at United, after cutting an isolated figure in the first couple of months.

Mourinho said: “We all knew how good he was. That’s why he was chased by many teams, I believe, and why we fought to have him here.

“Since day one, I was sure he was the right player, not just by the typical football qualities, but also by his mentality.

“We needed that – a little bit more experience and mental aggressiveness that I knew sooner or later were coming.

“I don’t like the January market, but it was now or never. Next season, after pre-season, being comfortable and adapted, he’s going to be great for us.”