Jonny Evans fired the visitors into a 21st-minute lead from close range before Ronald Zubar was sent off for two yellow cards.
Antonio Valencia then doubled United’s lead and Danny Welbeck made it three on the stroke of half-time.
Javier Hernández’s second-half brace added gloss to the scoreline as United pulled four points clear of Manchester City, who host Chelsea on Wednesday, at the top of the table.
“What’s significant today is it’s reduced the goal difference by five goals and that’s down to three now and it may make a difference at the end of the season,” Ferguson said after the game.
“I expect it [the title race] to go to the wire. Hopefully we achieve what we want to achieve.”
The United boss refused to read too much into Sunday’s result, but praised his side’s clinical finishing in front of goal.
“It [the performance] was OK, I don’t think it was anything special,” he added. “I think we’ve taken our goals well.
“The finish from Valencia was fantastic. Antonio is back in the team and his form was fantastic today. He’s made one for Danny Welbeck before half-time that killed the match.
“It’s difficult for them with 10 men, they were honest and kept plugging away but the 3-0 advantage was too much for them.”
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