The Red Devils came up against a battling Royals side, with Wayne Rooney grabbing the eventual winner in the 21st minute at Old Trafford.
Manchester City’s 2-0 defeat at Everton earlier in the day allowed Ferguson’s men to take a step closer to their 20th top-flight title.
But although the United boss admits their rivals’ loss took some of the “edge” off Saturday’s game, the Scot warned his side that there is still a long way to go.
“Maybe it [the City result] took a bit of the edge off the game,” Ferguson said.
“You don’t get points and medals for being complacent and we won’t be. I think the players are conscious of the importance of the games now and that concentration, which has improved, has helped us do that [in terms of keeping clean sheets].
“It wasn’t a great performance but where we are today is not down to today but the last six months. The team has shown great consistency and played a lot of great football.
“Our goal difference is big over City now – 13 goals. It’s a great position to be in but the only thing we can do is win our next game.”
Ferguson, whose side host City at Old Trafford on 8 April, added: “We expected a tough game. They’re down at the bottom of the league and it happens quite often when a team changes their manager, they get a reaction.
“It was what expected. They’re fighting for their life at the bottom of the league and they came here very determined.”
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