Bielsa took the blame for a scuffle which broke out moments before Leeds’ 89th-minute equaliser, saying he “lamented” his actions and regretted “allowing myself to behave like this.”
Tempers frayed on the touchline as Leeds winger Gjanni Alioski attempted to retrieve the ball from Millwall’s technical area for a throw-in with Harris’ side defending a 55th-minute goal from Jed Wallace.
Bielsa, who was facing up to the prospect of a first league defeat as United boss, waved his players away from the melee but then remonstrated with Harris and his assistant, David Livermore.
The Argentinian has cut a reserved figure during his early weeks in charge of Leeds but was visibly angered by the Millwall’s refusal to hand over possession.
Speaking afterwards, however, the 63-year-old said: “I take responsibility for this situation because I'm in football longer than my colleague (Harris). If you win or you lose it means a lot for us. Sometimes we behave in a way and then after, we lament our behaviour.
“I have the obligation not to behave like this and I shouldn't allow myself to behave like this. When you get more experienced, you should moderate your behaviour. That is why I apologise.”
The situation threatened to boil over again when Saiz ran 40 yards to celebrate with Bielsa and his backroom team after Jack Harrison snatched a draw with a minute of normal time to play but Harris revealed that he and Bielsa had cleared the air after the final whistle.
“It’s just football,” Harris said. “We should give the ball back quicker but we don’t because there’s two minutes to go and you’re 1-0 up at home. They then got excited when they scored a goal but I spoke to Marcelo downstairs and there’s no problem whatsoever. It’s fine.”
Bielsa’s preparation for Saturday’s trip to London was heavily affected by injuries to Kemar Roofe, Pablo Hernandez and Kemar Roofe, all of which arose in the week before the the trip to the New Den. Youngsters Tom Pearce, Jack Clarke and Ryan Edmondson were included amongst the substitutes and Adam Forshaw made his return from a broken foot bone by coming off the bench for the last 16 minutes.
United have now drawn three of their last four matches but remain unbeaten and at the top of the Championship after matching last season’s initial run of seven league games without defeat.
Bielsa admitted that the clash with Millwall had asked similar questions of his players as a goalless draw with Middlesbrough prior to the international break and said he was satisfied to take a point from both games.
“The main arguments of our opponent were throw-ins, corners and long balls,” he said. “All of them are legitimate but to impose our style we needed to do more complicated things. We couldn’t neutralise (the set-pieces) even though we prepared ourselves for them. But we did what we had to do to score.
“These two games, Millwall and Middlesbrough, were a challenge for us and we got two draws. We didn’t deserve to win either. But I don’t think it’s linked with the players who aren’t with us. I think it’s more linked to the development of experience and the style.
“We know that the players who aren’t with us are important players but I can’t use the fact of the players we had missing to explain why we didn’t win.”