#1 Exploit Chelsea's high defensive line
Maurizio Sarri prefers a high backline which leaves little space between the midfield and the defence lines. This also helps Chelsea in functioning as a better cohesive unit by stringing passes and maintaining possession, but playing defenders high up the pitch has its own disadvantages.
Mourinho will have the chance to exploit the space the Chelsea defenders leave behind them while playing high up the field. Also, the Blues tend to make individual mistakes which give the opposition the opportunity to make fluid counter-attacks. Sarri's men were left exposed many times in the game against West Ham United, which was a direct result of playing a high defensive line
Another point that needs to be noted is how Sarri has transformed David Luiz into a ball-playing defender who starts attacks from the back. Romelu Lukaku will need to pressurize the Brazilian incessantly when not in possession to stop him from building up play from the back.
Knowing that Chelsea will be aggressive right from the start and projecting that Mourinho will ask his men to sit deep and defend rather than foray forward, counter-attacks may be United's best chance of grabbing goals.
If they are going to score, then United's front three will have to be alert to exploit the Chelsea backline by finding spaces behind the defenders. They will also require flair and the cutting edge to transition to set up counter-attacks as swiftly as possible, coupled with clinical finishing to deliver the end product.