Macheda is on-loan at QPR for the remainder of the season.
"He's a big fan of him is Sir Alex," Warnock told a press conference. "He doesn't want to let him go. He thinks there's something there in the player and he's no thoughts about a sell-on if we'd like to buy him.
"He doesn't want to let him go and Sir Alex doesn't do that with many, unless he thinks there's something there."