Alexis Sanchez has not travelled with Arsenal for their game at Bournemouth, amid speculation of a January exit, according to Sky sources.
The Chilean, who trained on Saturday, has six months remaining on his contract and manager Arsene Wenger appears resigned to losing him before the window closes.
Arsenal take on Bournemouth at the Vitality Stadium in the first game of Nissan Super Sunday, live on Sky Sports Premier League.
Wenger on Friday admitted for the first time Sanchez is unlikely to sign a new deal at the club, while Manchester United manager Jose Mourinho labelled the 29-year-old a "phenomenal" player.
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Sky Sports News understands Manchester United are interested in beating local rivals Manchester City to the 29-year-old's signature, and it emerged on Friday that City are not prepared to pay Arsenal's £35m valuation.
Wenger last week suggested a bidding war would be beneficial to the Gunners if the club are to sell the forward, who came on as a substitute in Arsenal's midweek draw with Chelsea in the Carabao Cup.
Speaking ahead of kick-off, Alan Smith told Sky Sports: "It seems like a battle between the two Manchester giants,City and United.
"From Arsene Wenger's point of view, he'll want to be getting this out of the way as quickly as possible.
"It will almost be a relief once it is out of the way and he can concentrate on those players that he knows are going to be here for the foreseeable future."