Sacchi believes Napoli coach Antonio Conte would welcome Grealish's arrival.
He told La Gazzetta dello Sport: "Napoli? Antonio Conte knows how to play in Europe. He knows he needs to improve in one-on-one situations.
"He's looking for another winger; Grealish is being talked about. He wants to create numerical superiority on the flanks. It's the right way to break down opposing defenses.
"And then, with (Kevin) De Bruyne, he's significantly improved the quality in midfield. (Lorenzo) Lucca will be very useful as a replacement for Lukaku both in Italy and in the Champions League."
On Serie A overall, Conte also said: "The public demands entertainment, it's time the clubs listened to the needs of those who pay for the tickets. It's no longer like the 1970s or 1980s, when people didn't know what was happening abroad.
"Now everyone sees how the game is played in England, Spain, Germany, France, and Italian football must get on the same wavelength if it doesn't want to risk taking steps backwards."