Isak was forced off at half time in last weekend's 2-1 comeback victory at Wolverhampton Wanderers after sustaining an eye injury, but it has since been reported by the Daily Mail that the Swede has picked up a toe injury, making him a doubt for the Magpies' trip to the capital.
Fellow striker Callum Wilson (back) is one of four Newcastle players already in the treatment room along with Sven Botman, Jamaal Lascelles (both knee) and Lewis Miley (ankle).
The potential absence of Isak could see summer signing William Osula handed a start up front, while Eddie Howe may also consider using either Anthony Gordon or Joelinton as a central striker.
Joelinton, Bruno Guimaraes and Sean Longstaff have all started each of Newcastle's first four Premier League games in midfield, but now that Sandro Tonali is back in the fold, Howe may ponder handing the Italy international his first league start of the campaign.
A back four of Valentino Livramento, Fabian Schar, Dan Burn and Lewis Hall is expected to remain intact, while winger Harvey Barnes - who scored a stunning winner against Wolves last time out - will be pushing to start on either flank.
Newcastle United possible starting lineup: Pope; Livramento, Schar, Burn, Hall; Tonali, Guimaraes, Joelinton; Murphy, Gordon, Barnes
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