Spurs looked to be cruising after taking a 2-0 lead at Turf Moor on Sunday afternoon but a spirited fightback by the home side resulted in a 4-2 win for Brian Laws' side.
"I'm bitterly disappointed," Redknapp said after the match.
"At 2-0 we had complete control and looked like we would go on and score more, but it wasn't to be.
"The crowd were getting edgy with them and it looked almost too easy.
"But they got a goal back and in the second half they came out and they were excellent.
"They ran all over us at times, I thought they played fantastic, and we really were a shadow of ourselves. I've no excuses. A lot of the defending was poor.
"We've had a great season, I've been delighted with the performances during the year, but you always want to win," he added.
"I didn't come here just to have a jolly up.
"Maybe I should have made a few changes, one or two did look like they were running on empty a bit."