Ralf Rangnick has been warned his renowned training methods could be Manchester United 's undoing this season.
The German tactician, 63, famously demands his players press with intensity and progress the ball up the pitch quickly.
To get his United squad operating at the desired level, Rangnick reportedly installed a countdown clock at the club's Carrington training ground after he was appointed interim manager in November.
The former RB Leipzig boss has a rigid philosophy which dictates possession must be won back within eight seconds and a shooting chance created within 10.
This high-tempo, proactive style of play is almost entirely opposed to United's approach under Ole Gunnar Solskjaer, who was sacked last month after a run of five defeats in seven Premier League games.
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The Red Devils seemed to adopt their new instructions to good effect during Rangnick's first game in charge, the 1-0 victory over Crystal Palace.
However, they struggled to maintain their high work rate as the clash with the Eagles wore on, while there was a definite lack of energy in the subsequent 1-1 draw with Young Boys and 1-0 win at Norwich.
It will take a substantial amount of time for Rangnick to get his players firing on all cylinders, with this task made even harder by the busyness of the festive schedule and growing coronavirus concerns.
Indeed, Chris Sutton believes the United interim boss would be wise to avoid overburdening his players in training to lessen the risk of injuries down the line which could derail their Champions League hopes.
The former Chelsea and England striker fancies the Red Devils to overcome Atletico Madrid to reach the quarter-finals, but only if their squad is in condition come the first leg in mid-February.
"Rangnick is trying to implement his philosophy at United," Sutton, 48, told the Daily Mail.
"It’s been a good start in terms of results, though not entirely in terms of performance.
"Who knows what type of team United will be in February?"
He added: "Hamstring injuries might become a problem if Rangnick’s training sessions are as relentless as they sound.
"But really, we’d hope to see a much-improved United by the time they face Atletico, who aren’t the formidable defensive unit they once were. I’m backing Manchester United."
The Red Devils were drawn against Atletico in the last 16 on Monday after the initial ceremony - which pitted United against PSG - needed to be re-conducted due to a glaring blunder that UEFA blamed on a technical error.
