Rooney, who was pictured arriving at their Carrington HQ, was the notable absentee for United's main session ahead of Wednesday's Champions League quarter-final against Chelsea at Stamford Bridge.
As required by UEFA, United opened the doors of their training complex for the first 15 minutes of their pre-match session and Rooney, in the spotlight following his reaction to scoring a hat-trick at West Ham on Saturday, did not appear.
In the spotlight: Wayne Rooney arrives at United's Carrington training ground
There was no official word from the Red Devils as to the reason for the 25-year-old England striker's absence and it was still expected that he will play in the first leg clash in London.
However, beyond question is the fact that all eyes will be on Rooney when the striker does eventually appear after he was charged with using abusive language at Upton Park, which brings the potential for a two-match ban.
United must decide by this 6pm today whether to contest the charge which, as it presently stands, would rule Rooney out of Saturday's Premier League game with Fulham and the following weekend's FA Cup semi-final against Manchester City at Wembley.
Where is he? Photographers were denied a picture of Rooney at the training session
Preparations: Sir Alex Ferguson
There was good news for United though as long-term absentees Rio Ferdinand and Anderson both trained, raising the likelihood that they will be involved at Chelsea as Sir Alex Ferguson's men look to gain a positive result that would leave them well placed to secure a semi-final encounter with either Inter Milan or Schalke in next Tuesday's second leg.
Rooney is facing a two-game ban that will rule him out of the FA Cup semi-final against Manchester City after being hit by an FA charge on Monday for his foul-mouthed outburst at Upton Park.
The Manchester United striker has been accused of using 'offensive, insulting and/or abusive language' foraiming obscenities into one of Sky's touchline cameras moments after completing a hat-trick in Saturday's win at West Ham.
The FA's hardline decision to clamp down on Rooney comes in the week Sportsmail launched our Stamp It Out campaign, itself sparked by Premier League chief executive Richard Scudamore's demand for better player behaviour.
But it will enrage United boss Sir Alex Ferguson, already fuming at his own five-match touchline ban and fine for a blast at referee Martin Atkinson.
Swear box: Wayne Rooneytook the shine off his hat-trick with a foul-mouthed rant directed at the TV cameras
Alternatively,he can contest the charge or the severity of the punishment and have his case heard by an independent regulatory commission on Wednesday.
However, under the FA's new fast-track rules, Rooney would not be granted a personal hearing or be represented before the commission, which also has the power to increase the suspension.
United will make a final decision this morning but could be prepared to gamble on losing Rooney for an extra game against Newcastle in a bid for a one-game ban so he faces City.Ferguson is likely to respond at a press conference later today for Champions League clash at Chelsea.
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