Those who had previously sought to dismiss the poor results and even poorer performances as merely blips had nowhere to hide. Neil Lennon's own words made sure of that.
His honesty is as laudable as it is alarming. That he should feel compelled to tell any group of players wearing the Celtic jersey that they are bringing shame to it underlines how critical the situation at the club has become.
Lennon's willingness to tell it as it is, not only to the men in the dressing room but also to the assembled media, is the clearest indication yet that this is man who knows what is being delivered is simply not good enough. Not by a very long way.
Generally, the words spoken in a dressing room – especially at half-time when emotions are running at their peak – bear little relation to those relayed in the press room or trackside on radio an hour or so later.
By then, composure has returned, or at least the image of composure – even if, deep down, the anger continues to course through the man whose job is put on the line every time his players cross that white line.
The press conference can be the most demanding aspect of a match day for some managers. They know the men with the microphones and pens can sniff blood, and they must portray an aura of a man who is neither vulnerable nor wounded.
Lennon, however, does not play by the conventional rules. He has always opted for truth, not illusion. There is never any smoke and mirrors. He tells it like it is, whether it be to his players or the Press.
Sometimes, that is damaging in itself, as it can increase the pressure which is already at a point which would have men of lesser inner strength and resolve wilt.
When, a fortnight ago, he spoke softly and willingly in a corner of the cramped Tyne-castle press room just minutes after watching side lose 2-0 to Hearts, it was without prompting he offered the assertion that, if results did not improve quickly, he would have to consider his position.
Lennon may be, in relative terms, a rookie boss. But he has been around the game long enough, working under men he admires such as Martin O'Neill and Gordon Strachan, to know that such language would make big headlines and bring even more scrutiny upon the matches which were about to follow.
Now, after a two week hiatus for international action, the spotlight is very much back on Lennon following the club's fractious AGM and the horrendous first-half showing at Rugby Park.
Sure, his players did respond, fighting back to score three, second-half goals against Kilmarnock, indicating that they are pulling as hard for the manager as they claim to be when speaking individually and collectively to the media.
But, are they really doing enough? There were 13 minutes of the game remaining when they drew level, and the momentum was very much behind them. But, they could not go that extra yard to take all three points to narrow the gap on Rangers.
Psychologically, did they think that gaining parity with Killie was good enough when, in reality, catching the men from Ibrox is the real challenge?
More concerning, and what can't be forgotten amid the relief of not losing, is the fact that every Celtic player selected by Lennon for this game knew precisely what was at stake. Yet, they still contrived to go 3-0 down by half-time.
All of which smacks of a serious problem, if not in the heart of the dressing room, then at least in the heart and mind of the players.
The Lennoxtown training facilities boast everything a player could request. That includes mirrors. Instead of using them to check out how they are going to appear to the supporters camped at the gates waiting for autographs, the players should use them to ask themselves if they are giving everything they have to a manager who deserves nothing less.
If every one of them answers yes, then they are better liars than players.