Manchester United legend Gary Neville declared Manchester City are "far too close for comfort" to matching their rivals' famous treble.
Alex Ferguson's side made history in the 1998-99 season by winning the FA Cup, Premier League and Champions League, a feat not achieved by any other English side.
However, City remain in the hunt on all three fronts this season and, while manager Pep Guardiola has played down talk of a potential treble, the fight is on.
City hold a 3-0 advantage over Bayern Munich ahead of Wednesday's second leg of their Champions League quarter-final, and face second-tier Sheffield United in the FA Cup semi-finals at Wembley on Saturday.
In the Premier League, City sit four points behind Arsenal with a game in hand and take on Mikel Arteta's side a week on Wednesday at the Etihad Stadium.
As a result, Neville has admitted his concern that United's arch-rivals could match his club's historic achievement.
"I thought their Bayern Munich game was sensational. Bayern Munich were fantastic in the game in the first half and when Pep Guardiola said after the game he was worried, I could feel that as Bayern looked dangerous and sharp," he said on the Gary Neville podcast.
"He was resting players against Leicester because he knows he has to go to the Allianz Arena and it will be tough and he knows that. If Bayern get a goal, it is a bit like Anfield where they can go and get two or three.
"They've had a brilliant week, City. To win that game 3-0 and beat Liverpool 4-1, they're purring, they're playing well. They're serious now about it and they're in great form now.
"Rodri, Kevin De Bruyne and Ilkay Gundogan in midfield, the best midfield you can get. Up front, Erling Haaland, Jack Grealish and Riyad Mahrez are really settled now. They're hitting the home straight.
"The treble was mentioned last week, it's definitely on. They can win the European Cup, FA Cup and the Premier League.
"There's a long way to go, they can come up against a team that does them on the way: Real Madrid in the Champions League, Manchester United or Brighton in the FA Cup or they could lose to Arsenal at the Etihad, but they're very close to it. Far too close for comfort."