Hernández turned in Nani’s low cross on 17 minutes, and struck his second after being set up by Wayne Rooney, who increased the lead soon after. Fabio rounded things off with his first goal for United.
This is a big week in the title race with second-placed Arsenal playing Birmingham City in the League Cup final on Sunday. Sir Alex Ferguson’s team could be seven points clear by the time Arsenal next play, if United beat Chelsea on Tuesday.
Elsewhere, Jermaine Beckford struck twice as Everton, who beat Chelsea in the FA Cup last week, beat Sunderland 2-0. The win moves Everton into the top 10.
Just above Everton in the table are Newcastle, who were held to a 1-1 draw at home by Bolton. Chelsea loanee Daniel Sturridge scored his fourth goal in as many appearances for Bolton, while Newcastle played the last 30-minutes with 10-men after Ryan Taylor was shown a straight red card for a two-footed tackle on Johan Elmander.
It was a good day in the Midlands as both Aston Villa and Wolves got important home wins. Villa beat Blackburn Rovers 4-1 victors, while Wolves beat Blackpool 4-0. Those goals helped Wolves move out of the relegation zone on goal-difference.