José Mourinho will be backed in January to strengthen Manchester United if the right deal is possible in what can be a difficult transfer window for finding value.

The manager wants a central defender and goalscoring forward after trying unsuccessfully to sign one of each in the summer.

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More than £100m is potentially available. Mourinho was interested in Real Madrid’s Raphaël Varane before the start of the season and United were prepared to pay that level of money for the 25-year-old had the transfer been possible. The same degree of finance remains.

Leicester City’s Harry Maguire and Bayern Munich’s Jérôme Boateng were two other Mourinho targets at centre-back but United declined to pursue them as the board did not believe either was an upgrade. This caused the manager some disquiet and it is understood he will be supported in the winter window should a player who can improve the squad become available.

After the 2-1 win against Everton on Sunday Mourinho pointed to the lack of recent firepower from Romelu Lukaku and Marcus Rashford, highlighting how there has been only one goal from them in the past nine games.

Last January Alexis Sánchez was signed in a swap deal that took Henrik Mkhitaryan to Arsenal. The Chilean has been a disappointment but this has not lessened the willingness to enter the winter market.

Anthony Martial scored and won a penalty against Everton and does not realise how good he can be, according to Nemanja Matic, who described the 22-year-old as perfect for United.

Mourinho was minded to sell Martial in the summer but Ed Woodward, the executive vice-chairman, vetoed the idea. Matic said: “Anthony is a great player and he needs to understand that. He needs more confidence. He is still young and I think if he continues to score in the next game he will get that. If he reaches his top level he can be one of the best players in the league for sure. Sometimes I don’t think he understands how good he is.

“He is quick, he is good with the ball, he can run. He has everything that a Manchester United football player needs. Sometimes I don’t think he understands that. If I had his ability with the ball and I was as quick as him, then I wouldn’t pass to anyone and I would score every game. To be serious, he does need more confidence and this comes with results.”

Matic also worked under Mourinho at Chelsea so has a particular understanding of the Portuguese’s demands. “The manager speaks with him about it,” he said. “And I have told him [about how good he can be].”