Phil Jones said Manchester United have not given up hope of catching Premier League leaders Chelsea.
United's 11-match unbeaten run came to a shock end on Sunday when they lost 1-0 to Southampton at Old Trafford.
The defeat meant United dropped to fourth in the table and Louis van Gaal's men are now some 12 points behind Chelsea, who are two points in front of second-placed Manchester City.
United's 150 million-pound four-man attack looked blunt, but Jones believes it would be wrong to make a snap judgement on the team's title aspirations based on Sunday's defeat.
When asked whether the loss meant it would be hard to catch Chelsea or City, the United defender said: "No. You have seen teams dropping points. I think Chelsea were clear of City and then two games within the space of a week and they are back in it. That's how football changes.
"It's up and down. You just never know who is going to drop points. That gives us hope. There's always hope, but we have to worry about ourselves really rather than anyone else."
Jones also admitted that Manchester United are still getting used to playing with a back three -- after Southampton manager Ronald Koeman said that Van Gaal's tactics made it harder for the former Premier League champions to start attacks.
Centre-back Jones, who played in a back four under David Moyes and Sir Alex Ferguson and during his time at Blackburn, has been one of those most affected by the change in formation this season.
And the 22-year-old accepted United still make some mistakes in possession as they try and adjust to a different shape
He said: "Maybe we play that pass in the defence but we shouldn't. It's a learning curve. It doesn't just happen overnight. You don't just click your fingers and you are used to playing in a formation. It's like anything. But we are improving in training and we want to get better. That's the main thing."
Jones insisted that: "We have a back four or three. We are comfortable with both."
Koeman had suggested United's play was slower with their current shape, claiming: "You know that they have difficulties to build up with three centre-backs."
United have now only won one of their last five league matches and Jones said: "We have lost the game, the lads are disappointed but you have to move on quickly. You can't dwell on these results. We have done OK over Christmas. We would have liked to have picked up two more points against Stoke and Tottenham but now we need to get a bit of a run."
For the first time since 2009, United failed to record a shot on target at Old Trafford in the loss to Southampton but Jones pronounced himself unconcerned.
He said: "We were creating chances. Maybe we could have put them in but it wasn't to be."
Information from ESPN FC's Richard Jolly and Press Association were used in this report.