City boss Tony Pulis is closely monitoring Kightly's situation amid reports of a £2m bid already being tabled at Molineux.
Eustace played with Kightly at Watford and told The Sentinel: "When he came here he set the place alight.
"He did really well and was exactly what we needed at the time.
"He's quick, he's lively, he has a trick or two and has an eye for goal… he scored a couple of great goals for us.
"Even more importantly, he's a great lad around the dressing room as well, so I think he could be a great asset if Stoke get him."