The Rs paid the price for a sluggish display as Nedum Onuoha's own-goal and Diafra Sakho's second-half header gave all three points to the Hammers, who move up to seventh in the table, level on points with Arsenal and Liverpool.
Sky Sports pundit Gary Neville described the visitors' attitude as "diabolical" after the game but Redknapp refused to criticise his players' commitment.
"It wasn't great, that's for sure - that's his opinion. I've seen some diabolical performances of late as well but we won't go into that one," Redknapp said.
"We need to get them fitter. I've put a lot of faith into Sandro. Unfortunately he's had an injury and we need to get him fit.
"When he's fit he's a fantastic player - I had him at Tottenham, he's an excellent player - but at the moment he's short of fitness.
"The doctor came to me at half-time and told me he can only play another 15 minutes - I need players who can play 90 minutes.
"They've had injuries and missed training - we need to get everyone fit and ready to go."
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