Van Persie blazed one attempt off target but forced Cech to stretch and save with his fingertips from a 75th-minute snap-shot. The ball was spinning agonisingly towards goal but instead rolled against an upright with the Blues keeper scooping it away. However, the danger had not passed with Rafael firing into the six-yard box where Hernandez, coming back from inside the goal, touched home in predatory fashion.
TV replays showed the Mexican may have been fractionally offside when the full-back connected with the ball although, in real time, there looked at least two defenders between him and the goal. To Chelsea's credit, they refused to accept defeat as Ramires hammered a speculative effort over the top and Di Matteo introduced striker Daniel Sturridge for Hazard.
Hernandez volleyed over with four minutes left from a Young pass as United found holes in the Chelsea defence late on. Five minutes of injury time failed to provide any further addition to the scoreline although Valencia, unfairly cautioned for diving, screwed a poor finish wide following neat play by Hernandez. United still completed the job in professional fashion to narrow the gap at the top to a single point and end the capital club's unbeaten start to the league campaign.