Pedro scored within 30 seconds to give Mourinho's former employers the lead before Gary Cahill smashed in a second with Eden Hazard and N'Golo Kante sealing a resounding win in the second half.
But the Red Devils boss wants his side to focus on returning to winning ways in their upcoming matches following a tough run of fixtures.
He told Sky Sports: " In the first minute, you analyse the goal and you can see what happened - we made incredible defensive mistakes, individual defensive mistakes and you pay for that
" In terms of points, it's zero points - if you lose 1-0 or 4-0 you lose three points. We are six points from the top of the league and now we have to win matches
"We had a week where we have played two (title) candidates in Liverpool and Chelsea and now the other teams from the top five have to play among themselves, they have to draw and lose the points each
"We need to win our matches now, which is not easy but we play Burnley, we play Swansea and West Ham and we need to win matches to close the gap."
On his reception at Stamford Bridge, he said: "I was not expecting anything different and the crowd behaved in the normal way so.. nothing wrong."
He refused to elaborate on what he said to Chelsea boss Antonio Conte after the full-time whistle in what appeared to be a heated exchange between the two.
Source: PA