For Sunderland, the pressure to win promotion is on. 

With last season ending in bitter disappointment in the play-off final, after falling away in the chase for automatic promotion, Jack Ross is expected to deliver Championship football for the 2020/21 season - and nothing less will suffice.

And it had all been going well for the Black Cats in recent weeks. Five wins on the bounce in all competitions, including against Premier League Burnley in the Carabao Cup, had seriously lifted spirits and also lifted the club into upper echelons of the third-tier table.

But they crashed back down to Earth on Saturday, however, when they were beaten emphatically by promotion rivals Peterborough United at London Road.

Whilst it was an underwhelming showing, for the most part, Ross' side remained a match for their opponents, with Marcus Maddison's brilliance, lapses in concentration and individual errors leading to a 3-0 deficit.

However, it was a match that also showed that, for the most part, lessons had failed to be learnt from the previous campaign.

Ill-discipline was a factor that badly hindered their promotion chances last season and, if it continues, will do the same again.

With 20 minutes left to play, and with the Posh already three goals to the good, Sunderland were reduced to ten-men when Luke O'Nien tussled with Ivan Toney on the touch-line.

The Peterborough striker dramatically hit the deck after the right-back had swung at him in an attempt to shake-off his opponent's attentions.

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It may have been a harsh red-card, but it was also petulant from O'Nien and gave the referee a decision to make.

Six minutes later, they were down to nine. Striker Charlie Wyke went steaming into a challenge on Posh midfielder Josh Knight in nearly exactly the same spot. Whilst the result was a second yellow, it could easily have been a straight red.

Now, Jack Ross has to adapt his squad for three matches without O'Nien (pending any appeal) and one without Wyke.

Even if the former's card is overturned, it is a season quickly following a similar path to the last.

In 2018/19, Sunderland finished third highest in the League One booking charts and racked-up the joint-most red-cards.

That red-card total was eight, and with just six matches played this season, they are well on course to beat that total this time around.

They already sit in third this time around too with 12 yellow cards and two reds already to their name. This should be a big concern.

Sunderland have a squad capable of winning promotion to the Championship. There is no doubt about that.

However, if they fail to address their blatant problems with discipline, it is a campaign that will end in bitter disappointment once again.

It would have been no help seeing someone of captain Grant Leadbitter's stature lunging into tackles and getting in the referee's face on Saturday.

Change must, therefore, come from the top. Ross has to hammer home the message to his players that ill-discipline will not be tolerated and he will need help from the senior squad members to do that.

It cost them last season and they must not let it cost them again.