Morocco international Taarabt was said to be holding out for a close-season switch to Serie A giants Milan after spending half of last term on loan at San Siro.
But a move to Italy failed to materialise, and the 25-year-old has played just one minute of Premier League football for QPR this term.
And ahead of his side's top-flight clash with Stoke City on Saturday, Redknapp expressed concerns over Taarabt's continuing fitness issues after he limped out of training this week.
"Adel's twisted his ankle this week," Redknapp said.
"We had him in training and after 15 minutes he had to limp off again so we're back to square one with him.
"We just can’t get him fit - he keeps trying to come back on it and it’s going again. Do you rest him a few weeks?
“But then while he’s resting, is he going to put on weight? How are you going to get him fit? It’s such a difficult job with him.
"He needs to get his weight down and get it right so we get him fit to play."
However, despite Taarabt's problems, Redknapp insisted he sees the gifted playmaker as a key member of his squad.
"I'd like to have him available against Stoke as he’s got great ability," he added.
"We've got to get him fit and he's got to get himself fit - if he does that he could be a big asset to us this year."
