United's response was muted. There was a shout for another penalty when Patrice Evra was sent flying by Radosav Petrovic and man-mountain Samba got his head in the way of a Danny Welbeck drive but the Reds were showing little of the sparkle of the recent fixtures.
Phil Jones was denied a goal against his former club when he met a Nani corner but could only fire against team-mate Javier Hernandez. The Mexican tried to atone with a firm shot from outside the area that flew wide after some fine play by Evra before Nani lashed over after an intricate move inside the box.
Berbatov escaped after another grappling match with Samba at the other end but it was largely one-way traffic and the champions finally started to build a head of steam as half-time approached. Nani, the likeliest source of inspiration, finally extended Bunn with a snap-shot after controlling an Evra cross and the keeper also thwarted Hernandez at his near post as the pressure grew.
Frustrated by some time-wasting antics from the visitors, United played with more fire and the end to the opening 45 minutes at least showed promise of an improved display after the break with Samba hacking over his own bar from another dangerous centre by Nani. Sir Alex introduced Anderson for Hernandez at half-time and reshuffled with Rafael, Nani and Valencia all switching positions.