The Sun says City will keep tabs on Ghoulam after he impressed at the Etihad during the week.
Guardiola had made cover at left-back one of his top priorities for next summer.
And the recent long-term injury to Benjamin Mendy has made his need for reinforcements even greater.
City know Ghoulam is into the final year of his contract with the Serie A leaders.
That means he will be available on a free next summer.
Napoli could also be tempted by a cash offer for the Algerian, 26, in January as he looks unlikely to sign a fresh deal.