Athletic Bilbao's Kepa Arrizabalaga is another goalkeeper target for Chelsea, Sky Sports News understands.
With Chelsea resigned to losing Thibaut Courtois, who missed training for a second day on Tuesday, to Real Madrid before the deadline, the club are focusing their attentions on securing his replacement.
Stoke's Jack Butland remains their first choice because of the nature of the deal, according to Sky sources, which is expected to cost them £30m if they can act quickly.
But that price will rise the closer to the deadline it becomes.
Arrizabalaga would cost Chelsea much more, understood to be around £70m.
New head coach Maurizio Sarri is thought to be keenest on Atletico Madrid's No 1 Jan Oblak - but he would be the most expensive option due to his £89m release clause.
Meanwhile, Sky Sports News has been told that Stoke were keen on Joe Hart and Angus Gunn this summer, but both have now finalised deals to Burnley and Southampton respectively.
They now have no obvious replacement for Butland, should Chelsea make a formal bid.
There has already been discussion about a possible Butland switch at boardroom level.