Redknapp handed debuts to recent signings Mauricio Isla and Leroy Fer, while Matt Phillips replaced the injured Charlie Austin in attack, but they made a sluggish start as Nacer Chadli gave the hosts a 12th-minute lead.
Phillips then squandered a glorious chance to equalise when he blazed over Hugo Lloris’ bar after being put through on goal before Eric Dier, Chadli again and Emmanuel Adebayor netted to turn it into a rout.
Redknapp was disappointed with QPR’s performance against his former side and believes they contributed to their own downfall with a number of errors.
Redknapp told Sky Sports: "We didn’t play well today, we started sloppy I thought.
"In the first minute we could’ve gone one down when we gave the ball away and then we didn’t get out of it really.
"I thought we stood off them, didn’t really get close to anybody, didn’t really make a tackle.
"I felt we were disappointing in that side of the game. You’ve got to go and work hard and get after people if you’re going to get football results. I thought we lacked that bit of urgency."
Speaking of Phillips’ missed opportunity to equalise, Redknapp said: "It was a great chance.
"He did everything right, took the ball down fantastically but just couldn’t finish. That’s how it goes. After that we conceded from a corner.
"We conceded sloppy goals today. They’re a good side but we’ve got to do better – we need to improve to stay in this division.
"It doesn’t help when you go one down early but you’ve got to get after people and today I thought it looked as though a few of them hadn’t played a lot of games and were still a bit short of sharpness."
Redknapp introduced Nedum Onuoha for Richard Dunne in defence for QPR at half-time, a move which seemed to help bring an improvement from the visitors as they changed to a 4-4-2 formation.
Redknapp said: "They’re 3-0 up so they can take their foot off the pedal a little but it’s not about systems.
"It’s about people doing the basics which is working hard with and without the ball. Today I thought we were lacking in that department.
"Last week I was delighted even though we got beat 1-0 by Hull, I thought we played ever so well. I came away and thought ‘Yeah, I like the look of this’."
Redknapp also hinted that he may look to make further additions to his squad before the transfer window closes.
"We’ve brought a few players in but we're still maybe a little bit short in one or two areas that can be improved on but we’ll have to wait and see," he said.
"We’ve still got two loans up our sleeve as well – domestic loans – which are useful. The chairman’s over so we’ll see how we go."