Van Dijk, 25, joined Southampton from Celtic in the summer of 2015 and it is understood that his value has rocketed to £50m amid reported interest from Chelsea and Manchester City.
The Netherlands international again starred for his team in Wednesday's 1-0 success over Liverpool and Puel has claimed that the defender will continue to improve.
"He's a strong man, a strong player. He's physical, he's a technical player and we are lucky to have a player with his quality and his spirit also, because he is a winner," Puel told reporters.
"He gives always the example for the team, for the young players. I think this season he finds consistency and every game is a good performance and this is very interesting for him and us. I think he has improved a lot this season."
Van Dijk has scored four times in 27 appearances for Southampton this season.