The boss described it as the 'worst we've played since I've been at the club' as goals from Massimo Maccarone, Geremi and Joseph-Desire Job ended our 100 per cent home record this season.
"Disappointing doesn't sum up how I feel and how we all feel," said Glenn, whose day was made even worse by another glut of injuries.
"That is the worst we've played since I've been at the club," he added. "Yes, we've got injuries, but that was a very, very poor performance.
"Our lads have played well this season and worked exceedingly hard for each other.
"But we let our standards drop and Middlesbrough played very well. When you have a mis-match like that, and it was a mis-match, we were never going to get anything out of the game.
"We couldn't even pass the ball simple. We didn't work hard enough at them, didn't work hard enough at angles and want the ball and that's something we have to put right again.
"The spark just wasn't there. We've got to turn the corner quickly and it will take a lot of characters to do that."
Glenn Hoddle offered no excuses after Saturday's disappointing home defeat against Middlesbrough.