Benitez praised the 22-year-old's progression since moving to the North-East, but said that the club may have to "enjoy him" while he lasts in the team.
"I have no idea if there is a chance we can keep him after the end of the season, so I think at the moment we have to make sure we enjoy him while he is here," the Spanish coach told the Northern Echo.
"He has energy and pace, but it's more than that. He is a player who is comfortable on the ball. His delivery, his crosses and set pieces - he is somebody who is different and he is a player playing with confidence now.
"He has slotted in very well and, to be fair, the atmosphere between all the players is very good. He is a young player, he is quiet, but he has a good relationship with all the players. His confidence is good, and he has the possibility to express himself here. He wants to play football and is doing that really well."
Newcastle's win over the Saints took them to 32 points, five clear of the relegation zone.