United take on AC Milan on Wednesday at Old Trafford with a 3-2 first-leg advantage, while Chelsea trail InterMilan 2-1 ahead of the return fixture at Stamford Bridge on 16 March.
Second-placed Lazio closed the gap to three points with a 2-0 win at home to Atalanta, while Napoli reclaimed third from InterMilan with a 3-0 win over Palermo.