The Black Cats were consistently on the prowl last season, on their way to a seventh-place finish and Europa League football.
Draws against Arsenal, Man City and Liverpool, a league double over Chelsea and an away win at arch rivals Newcastle were particular highlights.
Bottom of the Premier League
Indeed, the Wearsiders only finished six points outside of the Champions League places.
So far in 26/27, they've remained unbeaten in the Europa League and are just two points from top spot in the table, but in the English top-flight, they've lost to Ipswich Town, Arsenal, Man City, Brighton and Bournemouth, drawn with Leeds United and Brentford, and beaten only fellow strugglers, Fulham.
At the time of writing, and ahead of their next league fixture against Coventry, who are just one point and one place above them, Sunderland sit rock bottom of the Premier League.
They've scored only six goals in their eight games, conceded 14, and have amassed only five points. So, what's gone wrong for Regis Le Bris' swashbuckling side?
Just six goals scored
Reinildo Mandava's red card against Arsenal won't have helped, nor Kevin Danso's against Bournemouth, though they're side issues to a more general problem within the squad.
The lack of goals is stunning. Brian Brobbey has scored three of the six in the league, with only Enzo Le Fee, Wilson Isidor and Nilson Angulo also finding the net.
For a team that could pass the ball so well, too, and often at pace, the fact that the vast majority of the squad are stuck around the mid-70 % range for pass completion currently has hit Sunderland hard.
Another standout stat is that Granit Xhaka is the only player to have made more than 100 passes that ended in the final third (183).
Lack of purpose and desire
If the team that Le Bris puts on the pitch aren't going to be on the front foot and confident in their accuracy and range, one of Sunderland's biggest problems is staring them right in the face.
The final ball also appears to be a problem at this point. Of the 108 crosses in open play so far this season (Premier League only), just 22 have found their target.
That lack of purpose extends to one-on-ones, with Sunderland collectively losing 149 of their 281 attempted aerial duels.
For ground one-on-ones, a handful of players have put in a decent shift and, for example, Xhaka has a 60.87% success rate in this regard.
Unfortunately, he and others have been let down by the majority, who have struggled to get their percentages above 40-45%.
No commitment
116 tackles have been attempted across the Black Cats' eight league games, with seven players (Xhaka, Noah Sadiki, Reinildo, Trai Hume, Dan Ballard, Nordi Mukiele and Le Fee) responsible for 87 of them.
It's the same story with interceptions made, as just a handful of players have got their hands dirty in this regard, and the squad as a whole have also lost possession on 1,100 separate occasions so far.
What does that say about the commitment and output of a number of those players pulling on the red and white stripes? It really is relegation form from far too many who are stealing a living at this point.
Even goalkeeper Robin Roefs can't escape scrutiny. He's only managed to make 15 saves in eight games, roughly two per match.
Time to get their act together
After the Coventry game, Sunderland have to play Chelsea, Aston Villa, Tottenham, Liverpool and Newcastle within the next month.
If they haven't got their act together by then, they're really going to struggle going into the winter fixtures, which include the festive calendar.
Perhaps it's the added pressure of having European football to deal with that has knocked the team out of its stride, but the hierarchy really should've seen that coming if there's any truth in that assumption.
Ultimately, the players got the club into their current mess, and they have to get them out of it.
If they're unable to rally themselves to do just that, and Le Bris loses his job as a result, it could take years for Sunderland to get back to where they were just a few short months ago.
How quickly things can change...