The centre-back made the move to Loftus Road from Anzhi Makhachkala in January for a club record fee of £12.5m.
However, Redknapp wants to keep the former Blackburn Rovers man as he targets an immediate return to the Premier League.
"I'd like to keep him, he'd be the best centre-half in the Championship," Redknapp said.
"He had one bad day at Fulham and everyone got on his case. He's a good player and we need him back playing.
"[But] I don't know what will happen."
QPR host Newcastle United on Sunday.