After reporting that the foot felt better after the game, Cahill underwent precautionary X-rays this morning and has now been referred to a specialist for a more detailed second opinion.
The midfielder missed the last third of the Blues' Premiership campaign last season and was used only sporadically as a substitute by Australia in the Asian Cup this summer.
He wasn't asked to jump on yet another plane to join the rest of the squad in the pre-season trip to the USA and stayed on Merseyside to continue his preparations for the new season, which kicks off in 11 days' time.
If, as Granada TV were reporting this evening, it is a repeat fracture of the metatarsal bone, Cahill could be out for another two months, news that would come as a crushing blow and a squad that will already be without striker James Vaughan following his surgery to correct a dislocated shoulder.
Manager David Moyes is hopeful of completing the signing of left back Leighton Baines for what is now being reported as a £5m deal with add-on clauses to bring the potential final fee closer to Wigan Athletic's £6m asking price.
Additionally, the acquisition of Alan Smith — a player perhaps closer in attributes to Cahill than anyone else linked with the club this summer — remains a possibility despite the growing queue of clubs — Newcastle and West Ham are the latest — looking for permission to speak to the Manchester United striker.