The England forward is understood to have apologised for his absence from Sunday's 4-0 defeat by Brighton & Hove Albion, even as Aston Villa continue to reject a series of bids from the Saudi Pro League club.
Watkins remains keen on the move to Saudi Arabia, and his departure now looks increasingly likely before the transfer window closes.
With Watkins' Villa career appearing to be entering its final days, the club have moved quickly on potential replacements, opening contact with AC Milan over a deal for Portugal international Rafael Leão.
Villa are currently exploring the financial details of a deal for the 27-year-old, who has been in talks with Turkish clubs in recent weeks and has attracted interest from a number of Champions League sides across Europe this summer.
Manager Unai Emery is keen to strengthen his attacking options having already lost Morgan Rogers to Chelsea in a deal reported to be worth around €137million. Rogers wasted little time making an impression at his new club, scoring on his Premier League debut in Chelsea's 3-2 win over Fulham on Monday — a result that will only have sharpened Villa's urgency to reinvest in the final third before the deadline.
Emery's frustration over the Watkins situation was evident when he addressed the striker's absence following the Brighton defeat.
Pressed on whether Watkins had refused to play, Emery offered little clarity: "This question is for him. I can answer only with my silence."
Asked whether the player could explain his stance himself, Emery added: "I think you can call him, you can call his agent and he can respond."
With Leão's arrival potentially offsetting the loss of both Watkins and Rogers, Villa's business over the coming days looks set to define the shape of Emery's attack heading into a season that also includes a return to the Champions League.
Leão has scored 80 goals and provided 65 assists in 291 appearances since joining Milan from Lille in 2019, winning a Serie A title along the way. New Milan head coach Rúben Amorim's 3-4-2-1 system does not naturally accommodate an out-and-out left winger of Leão's profile, a tactical mismatch that has left the Portuguese increasingly peripheral to the club's plans and opened the door for suitors including Villa.