QPR look set to be relegated as they head into Saturday's clash with Everton still seven points adrift of safety, with just six games of the campaign remaining.
Remy has nevertheless impressed since arriving from Marseille in January, and Redknapp believes he would be among the Premier League's leading scorers if he had been with the club all season.
Redknapp concedes that a player of such quality is unlikely to stay ay Loftus Road if they drop into the Championship, although no talks have yet taken place as everyone focuses on the fight for survival.
"I would have thought it would be hard to hang on to Remy. He was someone we were chasing when I was at Spurs," said the QPR boss.
"Every goal he has scored here has been a fantastic goal. He has five goals in seven games.
"Over the season he would get you 20 goals in the Premier League. And a 20-goal-a-year man is going to be hard to hang on to.
"We have to make sure we stay up if we want to keep him. That's the key, although I haven't discussed it with him or the owners."