Loic Remy put the already-relegated Hoops 1-0 up only for the under-fire Jose Bosingwa to hand Newcastle three points that secured safety.
First he needlessly tugged on Hatem Ben Arfa's shirt to give away a penalty, which the Frenchman powered home, before a calamitous moment resulted in Yoan Gouffran being left to roll in the winning goal.
Bosingwa, who was jeered by the home fans, was withdrawn at half-time and while Newcastle had to hang on after goalkeeper Rob Elliot saw red for a second caution the visitors got the points to frustrate Redknapp.
"They were horrendous goals, both of them," he said. "I thought it was a poor penalty and once we conceded the penalty we conceded another bad goal.
"It (crowd reaction to Bosingwa) was not going to help anyone. It was negative. He made a couple of errors but he didn't mean to do it and I took him off because we needed the crowd to be with us.
"People pay their money, we all get grief at some stages but it has been a miserable season."
Redknapp again insisted it is simply a lack of quality that has seen the west London club slip back into the npower Championship - where he thinks the current group would not even claim a top-half place.
"We are short of quality, it's nothing to do with character," he said. "This team would not finish in the top half of the Championship. It's going to be very difficult to shift some of these players."
- Sports & Recreation
- Jose Bosingwa
- Hatem Ben Arfa
- Yoan Gouffran