Phil Jones said Manchester United were a "laughing stock" under Jose Mourinho this season, but the Red Devils are "now heading in the right direction" with Ole Gunnar Solskjaer at the helm.
Mourinho was sacked in December amid United's poor run of form and reports of dressing-room unrest - star midfielder Paul Pogba at the centre of discontent in Manchester.
United were outside of the Champions League places and reeling following a 3-1 Premier League loss to Liverpool but the club have gone 11 matches without defeat in all competitions since Solskjaer's appointment as caretaker to climb to fourth in the table.
After Saturday's 3-0 victory over lowly Fulham, United loom as a legitimate threat in the Champions League ahead of Tuesday's first-leg last-16 fixture at home to Paris Saint-Germain and centre-back Jones is feeling confident.
"Everyone's got to take us seriously now," said Jones, who signed a new four-year deal with United this week.
"We might have been a bit of a laughing stock at the beginning of the season but we're certainly not now. We've proven that in the last 10 or 12 games. We're improving, we're still getting better.
"It was tough for everyone involved. The club, the supporters, everyone. But it's about becoming stronger and seeing that through.
"I've said it in the past, we've not achieved anything yet, we're under no illusions but we're heading in the right direction."
Pogba scored twice against Fulham at Craven Cottage, where Anthony Martial was also on target thanks to a fine solo goal.
United are a point clear of Chelsea and Arsenal, and nine points behind third-placed Tottenham after 26 Premier League matches.
"We knew we could get into the top four. It's a big statement from where we were. We just need to keep improving and keep picking up points," said Jones.
"Consistency is key in any sport and it's no different here. We're putting a run together, we need to keep momentum going and pick up points. It's a tough period coming up, but these are the games you want to play in, the games you want to be available for. Bring it on!"
