Rio Ferdinand believes it would be a "nightmare" for Manchester United if Liverpool and Manchester City were to share all four trophies they have competed for this season between them.
The former United man made the admission after City joined Liverpool in booking their place in the quarter-finals of the Champions League on Wednesday evening. City were held to a goalless draw by Sporting Lisbon at the Etihad Stadium but progressed after winning the first-leg 5-0 in Portugal last month.
Liverpool qualified for the quarter-finals after edging past Inter Milan just 24 hours earlier. They lost the second-leg 1-0 at Anfield but went through 2-1 on aggregate after their first-leg win in Italy.
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It means that Liverpool's hopes of winning the quadruple this season are still alive, following on from their Carabao Cup triumph against Chelsea almost a fortnight ago. City, meanwhile, can still complete a treble themselves and deny Liverpool any further silverware, with the Blues still pursuing the Premier League title, the FA Cup and the Champions League.
With the two Premier League clubs amongst the favourites to win Europe's premier club competition, as well as the FA Cup, Ferdinand has outlined how damaging it could be for United to see their two biggest rivals dominate every competition.
"That is such a worst case, worst case," Ferdinand told BT Sport. "That's the worst scenario I can imagine, Liverpool and City sharing all four of the trophies. It would be a nightmare [for United].
"I can't [see anything other than that]. I think Bayern Munich are the only team that could stop that, and that's a big if.
"I agree Man City, Liverpool [are too strong]. Chelsea, on their day, possibly on their day punch with them - over two games, I think Liverpool and City are too strong."
Alongside Ferdinand, working as a pundit for BT Sport, was fellow former United man Michael Owen. He believes City will prioritise Champions League and Premier League glory.
Owen said: "What I do think is that these four [trophies] will be Liverpool and City's between them. If Liverpool have two and City have two, ideally for Man City they'd probably want the Champions League and Premier League."
Currently, City sit at the top of the Premier League, six points clear of Liverpool, who do have a game in hand. Whilst admitting that they are doing the chasing, Ferdinand believes Liverpool cannot be discredited.
"You can’t count them out, they’re that good a team and on their day they will beat anyone; they've got the power, the resilience, the know-how," Ferdinand added. "It's all positive at Liverpool at the minute. Yes, they're chasing Man City but they're in touching distance."
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