Paul Merson believes the signing of Cristiano Ronaldo threw Ole Gunnar Solskjaer's Manchester United plan "out of the window".
Solskjaer has been sacked as Manchester United manager after an "embarrassing" 4-1 defeat at Watford, with Paris Saint-Germain boss Mauricio Pochettino the club's top target to take over next summer.
United have confirmed Solskjaer's assistant Michael Carrick will be placed in temporary charge, with the club also revealing their intention to appoint an interim manager until the end of the season.
Following a second-placed finish in the Premier League last season and the summer signings of Ronaldo, Raphael Varane and Jadon Sancho, United chiefs expected to see further progress made this campaign.
But in his latest column, Merson says United started the season in a worse place due to the signing of Ronaldo.
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'Ronaldo signing threw plan out the window'
I feel sorry for Ole Gunnar Solskjaer. He had a plan at the start of the season, having finished second last season. He's chased Jadon Sancho for a long time, got him in, and he's given Edinson Cavani another year.
You could see his plan: you play Cavani every other game, you have Sancho on one side, Marcus Rashford on the other, you have Mason Greenwood coming in and swapping around, you have pace, power, energy, youth, skill, the lot.
Then, just before the season starts, he gets given Ronaldo. I think he's thrown it all out of the window. From day one, they're not a better team with Ronaldo in it.
You don't go 29 games unbeaten away without playing a certain way, and bringing Sancho in gave them another weapon to play that way. With Ronaldo up there, you don't have that weapon to play on the counter-attack any more. And Bruno Fernandes was their best player last season - he's hardly had a touch this season!
It's all snowballed for Solskjaer. He had a plan, and the Ronaldo situation threw it all out of the window, just before the season started. They only went for him because they heard Man City were after him. It's not like United were calling Juventus to ask if he's available because Ronaldo is the missing link for United winning the Premier League. He isn't!
They thought: 'We can't let him go to Man City - it's bad enough them finishing above us every year in the league anyway!'
'Ronaldo is a legend, but Man Utd need a team'
Solskjaer tried to drop him against Everton in early October - people say he rested him, but they had internationals the week after! He was hoping they'd beat Everton to justify him keeping the same team. That backfired, and all of a sudden, he had to go back to playing him every week.
They chased Sancho for 18 months, they get him and he doesn't play a game. People are saying they didn't need Sancho, but he was perfect for the way they played counter-attacking football. Now they can't counter-attack, and the plan completely and utterly went out of the window.
It's a problem going forward. The fans love Ronaldo, he's the king. Don't get me wrong, he's been one of the best players in the world, but this is the Achilles heel. The bloke is a legend, with the records he's put up, but that's not today.
It's alright people saying: "He's done his job, he's scored goals." But United need to play as a team to win trophies, not have someone who stands up front and puts the ball in the net 20 times a season. They need a team.
He's a legend. I'm not having a go at Ronaldo, and he'll go down as one the best to ever play football.
But I got shot down from day one on Transfer Deadline Day. I got slaughtered for saying they were further away from winning the league the moment they signed him than they were before. It's not Solskjaer's fault - Solskjaer didn't buy him!
I think they need to find a position for him, and maybe even give him a free role. I don't know if you can keep him in the team, I don't think they're dominant enough in midfield, and without Raphael Varane in defence, they're all over the place.
'Why wait to bring in permanent boss?'
To get beat like that at Watford is embarrassing. Forget about the Harry Maguire sending off. Even in the first half, they got slaughtered. You would have thought Watford were playing on a downhill slope, with the wind behind them. It was that one-sided.
They're talking about bringing in an interim manager until the end of the season. Why? This is a lot of hard work before United challenge again, it's not about steadying the boat.
They need to get a manager in now, no matter how much they cost. You pay £70m, £80m for a player, but they need a manager.
If you get someone in the summer and it doesn't start well, they'll be saying: "It's not my team, I couldn't get this player or that player." The new manager has got to have a clear-out as early as possible before the season starts next year.