The reigning Premier League champions slipped to an eighth defeat of the season on Saturday following a 2-1 reverse at Stoke City and trail leaders Arsenal by 15 points.
With the title seemingly beyond United, the priority now is likely to be claiming fourth place and making up a seven-point gap on old rivals Liverpool.
Smalling has acknowledged the onus is now on United and has called on the players to stick together following a fifth loss in eight games in all competitions in 2014.
"We've got to go into it as if we need to win every game," said Smalling. "We're the ones who have to catch Liverpool.
"So we've got to win the points and put the pressure on them. We've not done ourselves any favours with losses like this.
"It seems as if we are taking one step forward and then one back. But we need to stick together and really get into the next game because time is running out to pick up these points.
"It is only us players who can really get us out of this muddle and so we really need to stick together.
"We don't really talk about the Champions League, but I think we all know that's the minimum we need to aim for."
Smalling is also hoping United's luck starts to turn after fellow defenders Jonny Evans and Phil Jones went off injured in the first half at the Britannia Stadium, and Stoke took the lead through Charlie Adam's deflected free-kick.
The England international added: "You get injuries, you get certain decisions against you, you get deflections. I guess it's how the game goes.
"There have been a few deflected goals this year which have really not been down to us. Hopefully it will turn in time because we are due some good fortune.
"It was massively frustrating. We played quite well for large parts of the game. On another day the chances we had might have gone in.
"We pressed for the whole second half, we had a lot of the ball but it wasn't going for us."