Chelsea managed to win against Liverpool before Nani’s goal at Sunderland secured three points for United on Sunday.
The title race will now go down to the final day of the season when United face Stoke and Chelsea face Wigan.
“All we can do is win our game next week,” Ferguson told Sky Sports.
“Obviously I wouldn’t say it’s a sealed result against Wigan by any shadow of a doubt.
“They’re a good team, they’ll have a go and you just never know. It’s a crazy game.
“Maybe we are clutching at straws a little bit. It is important for us to win in front of our home fans and play the right way.
“It would be an incredible achievement for us. At the least we have stretched it (the title race) and kept the nerves going.”
“One-nil is not a healthy score away from home,” the Scot added.
“It was perhaps due to careless finishing. It looked that way. There were a lot of great chances. But we got there, that is important.”