Paolo Di Canio blamed his players for lack of desire and commitment after Swindon slumped to their first home defeat in over a year, losing 1-0 to Leyton Orient.
Lee Cook's 59th-minute goal consigned Town to their third defeat in six days after a 4-1 league loss at Preston on Sunday and a 1-0 reverse in midweek in the Johnstone's Paint Trophy to local rivals Oxford.
Town boss Di Canio said: "After two or three games I have discovered that my players do not have the quality to improve. I did not mind losing the record, it was bound to happen one day, but it was the way we lost I did not enjoy. There was not the desire or the 100% commitment.
"After this week's results I think I have over-estimated my players. It was an empty performance in terms of heart but I could not imagine we would lose in this way.
The Italian added: "I have to say that we brought in six players in the summer and then another five recently so it takes time to settle into a team.
"The Leyton Orient players when subbed were taking two minutes to get off the pitch and it was a bit like it is in Italy."
Orient boss Russell Slade was delighted it was his side who ended Swindon's long unbeaten run at the County Ground.
He said: "Our dressing room was a happy place to be. This result was coming for some time. We took the game to them and created two good chances in the first half and I think we always looked likely to get a winner.
"Swindon are a good side and will bounce back. This was the first time they have lost at home since August 2011 and the record was there to be broken and I am pleased it was us who did it.
"We have two home games coming up to make the most of this result and things are looking a lot brighter."