For a moment, you really did think that Sunderland could make the impossible look, well, just about possible.
A big win at Highbury Stadium was always needed to keep slender hopes of automatic promotion alive and for much of the first half, it looked like it might well be on the cards.
They played with control, quality and tenacity.
In short, everything that was missing in the second half that has to serve as a significant wake-up call ahead of what will unquestionably be a tough play-off campaign.
This was a night when both the best and worst of this side were on show.
For 40 minutes Fleetwood looked dazed and confused. Their midfield and defence were pulled out of position and all over the pitch, not knowing which runners to track as the away side played with fluidity and verve.
It was the 'relentless' Sunderland that Rochdale Brian Barry-Murphy spoke about a few weeks ago, at the point when it looked like the Black Cats were set to surge towards automatic promotion.
They established dominance in the centre of the field and used that to get their dangerous wide players into excellent positions.
Barton could only watch on as his side wilted. Chances were missed, and at half time there was that sinking feeling, knowing that Fleetwood could not possibly be so bad in the second half.
Barton bolstered his midfield with extra experience and they began to press well.
All of a sudden the back four had few option son the ball and it was all rather aimless, balls launched upfield with no one getting on the end of them.
Fleetwood created little, Jon McLaughlin barely having a save to make, but their two goals did reflect their general superiority.
Jack Ross cut a frustrated figure post-match and little wonder.
At a crucial time of the season he is still searching from greater control and consistency from his players.
Will Grigg looks desperately short of confidence. At left-back Bryan Oviedo's form continues to fluctuate from match to match and Chris Maguire, whose quality and vision makes him key to any success in the final weeks, is still searching for sharpness after injury.
Sunderland, who looked so well set at the start of this month, have now one just one league game in six.
It has been a punishing schedule right throughout the season and especially in April, but this failure to seize the advantage in games and apply the finishing touch has been a recurring theme.
Nor have they been ruthless enough in defence when the tide has turned.
Luton Town and Barnsley's automatic promotion has now been confirmed and no one can say it is not fully deserved.
They have been meaner defensively and more clinical in front of goal.
In recruitment especially, Sunderland will have much to reflect on when this season comes to an end.
For now, they have to establish themselves as the best of the rest.
At Fleetwood, as it has been for so much of the season, they showed more than enough to prove they are capable of that.
But this second half has to serve as a significant wake-up call.
One more showing like that could condemn them to another season in the third tier. The stakes really are that high now.