Jose Mourinho did not think Chelsea would choose to strengthen Manchester United’s squad by selling them Nemanja Matic.

The Serbia international, who joined his former Chelsea manager Mourinho at Old Trafford in a £40million last month, already looks a shrewd investment by United and was named man of the match in Sunday’s 4-0 win over West Ham.

Though he didn’t get on the scoresheet, it was the anchorman efforts that got United their first goal of the campaign. The 29-year-old outmuscled Pedro Obiang in midfield before releasing Marcus Rashford, who used Matic’s run as a decoy to slip in Romelu Lukaku for the opener.

Matic also won four aerial duels, two tackles and completed 86 per cent of his passes as West Ham were put to the sword, earning high praise from his manager, who is still surprised he was able to pinch a key player from a potential title rival.

​Mourinho said: “It depends on what was happening behind doors [at Chelsea], of course with Chelsea [they have] the money, but I know that I brought him to Stamford Bridge because I thought he was a player with special qualities and since I left I always felt he could be a perfect player for us.

“But I didn’t disturb him, or Chelsea. I didn’t think it was possible unless something special was happening, and it looks like something was happening because his agent said we could have him, we would just have to pay.”

Since Matic’s departure from Stamford Bridge, where he won two league titles, Chelsea boss Antonio Conte has intimated that he was not entirely happy to lose the midfielder, despite having signed Tiemoue Bakayoko as a new partner for N’Golo Kante.

“The importance for me about this player because, I repeat, he's a really good and strong player - and important for our team,” Conte said.

“Sometimes you must accept this crazy transfer market and sometimes you must accept different decisions. But I repeat for sure he is a great loss.”