The 23-year-old has recently been strongly linked with Tottenham and Manchester United.
Le Tissier believes it would be a “big blow” for the Saints if they were to lose the winger this summer.
Le Tissier said: “It would be a big blow if he left. He’s been very good for us.
“He’s possibly not consistent enough would be my only reservation for him to go and play for a top-four team. He’s a little bit hit and miss.
“But in his first season he did very well, got into double figures with Premier League goals and he’s very rarely injured.”
