Phil Smith's verdict: Making sense of Sunderland's heavy defeat and what it means for the Black Cats

That’s to say, whatever you think about Jack Ross and his team, this is something that has just not happened in the 14 months or so since this League One journey began.

It was not only the heaviest defeat of his reign, but the first time they have lost by three goals.

Remarkably, in 69 competitive games since he took charge, they have only lost by two goals on two occasions.

One was against Portsmouth, when the Black Cats had to play the vast majority of the second half at Fratton Park with ten men. At one stage they reduced the deficit to one and threatened a shock comeback.

One was in the Carabao Cup against Sheffield Wednesday, and even then a young side competed well against Championship opposition.

So any analysis of this utterly wretched afternoon has to try and answer the following question: an aberration, or a sign of structural problems?

It was a game that felt as if it had two fairly distinct parts.

There was the game before Peterborough United’s second goal, and the mess that followed.

There had been little between the two sides in what had been a cagey opening 50 minutes. There had been much talk of the attacking talent possessed by both teams but for the most part they cancelled each other out.

At the break Sunderland had spent more time on the ball, and Peterborough had created the most attempts on goal, though most of those came in an early flurry before the away side settled down considerably.

The Black Cats did not create much, just lacking quality in their final ball.

Defensively, they looked resolute enough, Alim Ozturk and Jordan WIllis coping with a lively and impressive front two in Ivan Toney and Mo Eisa.

They went behind to a moment of individual inspiration, Marcus Maddison intervening as perhaps he was fated to, given the remarkable level of noise that has surrounded him this summer. There has been more said and written about the boyhood Black Cats fan than some members of the current squad.

Sunderland responded relatively well, Marc McNulty forcing a save from Christy Pym just before the break. By the admission of Peterborough’s players and manager, they had not played all that well.

True enough, the Black Cats had not created much either. It was a distinctly average contest between two sides seemingly very conscious of the threat the other posed.

Sunderland started the second half well, and were threatening an equaliser when Peterborough scored their second. It was against the run of play but a fine counter-attacking strike.

The composure was superb, from the pass from Mo Eisa that opened Sunderland up, the clever play around the edge of the box and the emphatic finish from Josh Knight.

For the most part, Sunderland have not played in particularly high-scoring games in this division. More often than not it has been their ruthlessness in front of goal that has been the difference.

Here, the tables were ruthlessly turned.

That was the first phase of the game and it was the one that followed that arguably is a greater cause for concern.

Ross took responsibility, saying his substitution, replacing Lynden Gooch with Will Grigg, had been designed to chase the game.

Just over a minute later it was three.

It was another goal marked by some poor defending, absolutely, and also some impressive poise in the final third from Peterborough.

Two red cards followed in what was a loss of shape and discipline that we have not really witnessed from a Ross side.

Yes, there were dismissals last season, but many of them were deeply contentious, often overturned and the side often battled through them to get something out of the game.

In fairness to Luke O’Nien, Ivan Toney’s reaction looks worse with every replay.

Charlie Wyke’s second yellow was reckless, and a yellow for Max Power followed as he kicked the ball away in anger at a refereeing decision.

Sunderland did regain their composure enough to see the game out without further damage, but plenty had been done by then.

This had been an opportunity to turn a good start to the season into a quite excellent one.

Instead, everyone will have to dwell on this bitter disappointment for a full two weeks.

In truth, whether this was an aberration or something deeper is a question that can’t be answered until we are deeper into the season. It was concerning, and yet not as poor a display (for the opening hour at least) as what we witnessed at Portman Road.

Six games into the season, Sunderland are relatively well poised.

Two points off the top, having played three sides who will almost certainly be in the top eight come the end of the campaign.

It’s a small sample, but their win % for the campaign is 63, and that includes a contest with an established Premier League side. So any assessment of this defeat must be balanced against the five wins that preceded it.

It’s up to the Black Cats in a busy September to prove that this was an exceptional result.

It will have stung to be ultimately so outclassed in the final third, and it goes without saying that a firm reaction is a necessity.

For Ross, it throws up questions over his side just when it looked as if a settled XI was beginning to take shape. It will be fascinating to see who gets the nod when Sunderland travel to Accrington Stanley on September 14th.