José Mourinho has extended his Manchester United contract by a year to at least 2020, saying he is “honoured and delighted” to stay at Old Trafford.

There had been speculation that Mourinho may not extend his time at United but, in a week that has seen the signing of Alexis Sánchez, both the owners and manager were all smiles.

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Mourinho said: “I am really honoured and proud to be Manchester United’s manager. I would like to say a big thank you for the recognition of my hard work and dedication. I am delighted they feel and trust I am the right manager for this great club for the foreseeable future.

“We have set very high standards – winning three trophies in one season – but those are the standards I expect my teams to aim for. We are creating the conditions for a brilliant and successful future for Manchester United.”

There was, however, confusion over Sánchez and whether the player had inadvertently missed a doping test during the transfer from Arsenal to United. Widespread reports – following on from an initial report in Spain – said the Chile international may have fallen foul of the Football Association’s “whereabouts” rule by allegedly not being present for a test on Monday.

However, that was the day he was completing his high-profile switch from London to Manchester, opening the door to the possibility of genuine confusion as to his whereabouts.

There is no suggestion of wrongdoing by Sánchez or the clubs. Both Arsenal and United declined to comment, as did the FA. As part of the FA’s anti-doping guidelines, players are advised to notify the governing body if they are due to be absent from a scheduled training session. Manchester City and Bournemouth were both fined £35,000 last season after failing to ensure their whereabouts information was accurate on three occasions within a 12-month period.

On Sánchez, Mourinho said he was “one of the best attacking players in the world” but admitted the signing had very little to do with him.

“Sometimes managers can take responsibility for signings but my contribution for Alexis to be here was zero,” he said. “That was [executive vice-chairman] Ed -Woodward’s work after the green light from the owners.”

Confirmed in the squad for tonight’s FA Cup tie at Yeovil, Sánchez arrived at Old Trafford in a straight swap with Arsenal for Henrikh Mkhitaryan, a deal Mourinho described as “fantastic” for both clubs even if the Chilean’s reported wages of over £300,000 per week caused a few jaws to drop.

“Honestly I think it is a fair deal,” Mourinho said. “I cannot describe it as cheap but it is not expensive either when you put the numbers into perspective.

“The money we are paying in wages instead is according to his quality and, something people often forget, in acknowledgment of the risk. A player who allows the end of his contract to approach takes a risk. He is not protected by another two or three years of a deal, just imagine if he had picked up a similar injury to [Everton’s] James McCarthy.”

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Mourinho believes both clubs have done good business. “I lost a fantastic player, so did Mr Wenger,” he said. “Mkhi has gone to a fantastic club and Alexis changed from a fantastic club to a giant club. I believe Mkhi is going to be even better than he was with us. He has had one and a half years in England now and he should fit in with the way Arsenal think.

“I have known Alexis for many years. I was in Italy when he was at Udinese, I was in Spain when he was at Barcelona and in England when he was at Arsenal.

“He can play on the left and on the right, as a striker and behind the striker. Alexis has been successful in every role, in every country, for every manager. We want the best players possible and he is one of the best attacking players in the world.”

So is Cristiano Ronaldo, though Mourinho was unwilling to add to speculation that a possible return to United might be on the cards. “I think with the moment Real Madrid are having now I should be the last one to add fuel to the fire,” the United manager said. “I care about the club, I worked there for three years, so to put water on the fire instead I would say Cristiano is the kind of player every manager and club wants but only Zidane and Real Madrid can have him.”