Chelsea will open a 12-point lead over the champions if they win at Stamford Bridge in the second of our Super Sunday games.
Defeat for United would be a fourth in five games, but Jose Mourinho has been careful not to write off Sunday's opponents, and the message has got through to Cahill.
He told Sky Sports News' Weekend Warm-Up programme: "You would have thought it'd be a lot tighter, but Manchester United are obviously having a little blip in terms of results.
"It's not gone quite to plan, but they're obviously still a strong outfit and for us it's going to be a tough game.
"I don't see it as any sort of crisis - they've got a fantastic manager, great players. As a footballer you sometimes have a few weeks or a month when it doesn't quite go to plan and then you get back on track. I see them being no different.
"They are flush with talent in the squad - that's why I don't see there being any dramas. They've dropped more points than they would have liked, but the game's going to be just as tough for us and I see them turning the corner soon."
Chelsea v Manchester United is live on Sky Sports 1HD on Sunday, kick-off 4pm