Wayne Rooney has voiced his concerns after Manchester United's first defeat under Ralf Rangnick left the club playing catch-up in the race for the top four.
The former United forward, who is currently in charge at Derby County, accepted the decision to move on from Ole Gunnar Solskjaer was probably the right one.
However, just a few games into the reign of interim manager Rangnick, Rooney questioned whether the German's lack of experience taking charge of top sides meant the Old Trafford job represented a different challenge to those he was used to.
And Rooney's comments came into sharper focus after the defeat against Wolverhampton Wanderers, with the result prompting questions from other directions about the shape of the team under their new boss.
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Joao Moutinho scored Wolves' winner at Old Trafford, and visiting manager Bruno Lage was able to calmly explain after the game how his team got the better of their hosts after his opposite number admitted "a question of balance" is holding United back.
“The most important thing for us is to see where the full-backs are, to find the spaces, when they are defending and when they are attacking, to see where they are," Lage told Sky Sports after the game.
Lage's side were able to thrive by ensuring every player understood the system, and Rooney's concerns suggest this is an area where United still need some work.
“I was at [Rangnick's] first game against Crystal Palace and I thought they looked very good," Rooney, who has been to a number of United games this season, told The Athletic.
"My only concern, with that shape, was that when you come up against better teams — Liverpool, Man City, Arsenal — you could get punished.
"The most important thing is that the players need to buy into it. He needs to get them working as a group rather than as individuals.”
"I think it had got to the point with [Solskjaer] where everyone could see it was coming to an end," he admitted, having seen the Norwegian dismissed in November off the back of a 4-1 defeat at Watford.
"With the new manager now, you don’t know.
"I’m sure it’s a lot different to anywhere he has managed before. There’s a lot more pressure, managing a lot of high-profile players."
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Rooney's comments come as pundit Jamie Redknapp accused Rangnick of "making up systems" during the defeat, which came courtesy of a late Joao Moutinho goal.
“We talk about managers coming into the game, and Rangnick came in with this famed 4-2-2-2 system," the former Liverpool midfielder said.
"It doesn't work if you don't have the right players. You have to play the right system. Then he went to a three at the back, a 4-4-2, and at the end I think he was making up systems.
"There was no real identity of how they were trying to play. The Watford performance was a real low, but I'm sure the United fans thought at least they were good going forward.
“There was nothing today. When you watch Man City and the best teams, they have control of the midfield. United never had that."
United's defeat was their first since Rangnick took over, as well as being the first time under the interim manager in which they have failed to find the net.
The result leaves them seventh in the table and four points adrift of the Champions League places, though they have a game in hand on Arsenal and West Ham United above them.
