Manchester United midfielder Juan Mata has urged his side to stay strong in the wake of their 4-0 defeat to Chelsea at Stamford Bridge on Sunday.

Jose Mourinho's return to his former club soon turned into a nightmare for the visitors, with Pedro scoring inside the first minute to send Chelsea on their way to a resounding victory.

Mata, who was also facing his former club, acknowledged that his side paid for their slow start but stressed the importance of unity ahead of their EFL Cup clash with Manchester City on Wednesday.

"Things got complicated since the first minute. By conceding an early goal the game we had in mind changed completely, and from that moment we weren't able to come back. Chelsea had a much better start than us and we paid dearly for it," he wrote on his weekly blog.

"Once they scored the second goal, we tried to control the game a bit more by keeping the ball in Chelsea's half of the pitch, but obviously they were feeling very comfortable in a compact defence, and every time we lost the ball they had an opportunity to initiate a dangerous counter-attack. We created some chances to score and get into the game, but I had the feeling that whenever we were close to doing that, we were punished with another goal.

"But we must carry on. Luckily, in three days we have a very important fixture, and as from now we must focus on this new opportunity to get better. It sounds like a cliche but it's true: when we win and everybody praises you it's easy to be united and celebrate together, but it is now, after such a defeat, when we must remain mentally strong and keep going. Together we win and together we lose."

The defeat leaves United seventh in the table, already five points off the top four.