The 20-year-old forward, who was left out of Chelsea's squad list for Monday's Premier League opener against Fulham without even being handed a shirt number, is understood to be considering interest from clubs in Italy, Spain and Germany, with proposals varying between loan and permanent terms.
Napoli are among the most advanced suitors, seeking to sign Guiu outright rather than take him on loan, and have separately agreed a season-long loan for Chelsea defender Benoît Badiashile as they build out Antonio Conte's squad.
Guiu joined Chelsea from Barcelona for £5million in 2024 and is now valued at around £25million despite finding regular football hard to come by, managing three goals in 16 appearances across all competitions last season.
He is not part of new manager Xabi Alonso's plans for the campaign ahead, and his departure would form part of a broader trim of Chelsea's forward line as the club looks to balance the books before the deadline.
Napoli's interest is not limited to Guiu. The Serie A side have also looked at fellow Chelsea forward Nicolas Jackson, though a £65million valuation has so far put them off pursuing that deal further. Jackson has also drawn interest from Aston Villa and Atletico Madrid, while Liam Delap — priced at £50million despite scoring just twice last season — has attracted attention from Everton, Nottingham Forest and his former club Ipswich Town, as well as Serie A side Como, who have already signed Trevoh Chalobah from Chelsea this window.
Ipswich are understood to hold a sell-on clause from Delap's £30million move to Chelsea last summer, meaning any sale would trigger a further payment back to the Championship club.
With Guiu, Jackson and Delap all potentially heading for the exit, Chelsea will lean on João Pedro as their undisputed first-choice striker this season. The Brazilian, signed from Brighton last summer, has been rewarded for a stellar debut campaign with a new contract running to 2034 and has inherited the number nine shirt vacated by Delap, who now wears number 12.