Sanchez was due back at Arsenal on Sunday, but his return to England has been delayed by at least 48 hours after he caught the flu, revealing the illness with an social media picture of himself huddled under a blanket with the caption "sick".
However, Monaco owner Vadim Vasilyev has reportedly had enough of selling for one summer, meaning Arsenal may now be forced to abandon their pursuit of Lemar and look elsewhere as Arsene Wenger attempts to build a squad capable of returning the Gunners to the Champions League.
"There's no development - he is staying, of course".
Arsenal manager Arsene Wenger has said many times that he would refuse to sell Sanchez and rather see the former Barcelona man leave on a free transfer when his contract expires.
"We have been in touch with both him and his doctor and he will be back as soon as possible", said Wenger after this comfortable victory before categorically stating: "He is staying".
Sanchez is in the final year of his contract at Arsenal and has been repeatedly linked with a move to Manchester City or Paris Saint-Germain. "That's why I prefer my side [of the story]".
But captain Mertesacker, speaking after Arsenal's 5-2 Emirates Cup win over Benfica told reporters: "I think everyone wants him to stay because he's a player with the X-factor and in the last season he has played some incredible games and he was our dominant goalscorer". He's flying back as soon as he's in a position to fly back - he has the flu. It is a secret conversation.
Wenger also refused to say if he would make another bid for £50 million-rated ($65 million, 56 million euro) Monaco winger Thomas Lemar after having several offers rejected. We speak in English.