Aberdeen conceded three times after half-time at Easter Road to go down 3-0 to Hibs.
The result left Derek McInnes’ team fourth in the Premiership after they dropped below Motherwell, and ended a run of six games unbeaten.
After they’d gone a goal down to Martin Boyle’s opener, McInnes quickly made a triple change with Ryan Hedges, Dean Campbell and Curtis Main coming on for James Wilson, Zak Vyner and Shay Logan.
He moved from a 4-2-3-1 formation to a 3-4-2-1.
However, it only got worse for Aberdeen with two more Hibs goals, which both started on the left side.
While all the home goals were poorly defended with players giving the ball away, out of position or failing to get close enough, Hibs’ second exposed huge gaps in the three-man backline, with Scott McKenna and Ash Taylor sucked towards the ball.
A pass in behind left just Andy Considine – perhaps not fully fit – in a foot race with rapid winger Martin Boyle and the result was predictable.
Crisis in midfield
Aberdeen will be desperate to get Funso Ojo and Craig Bryson back in midfield.
There is always a risk lifelong central midfielders will dominate and play around the likes of Zak Vyner, normally a defender, and young sub Dean Campbell, given their lack of experience and Hibs did.
There also has to be an improvement in the distribution from midfield – look at Scott Allan’s wonderful, incisive passing for Hibs’ opener.
Next up for Aberdeen is a very winnable home meeting with Hamilton Accies, then the tough task of Celtic at Parkhead before closing the year with Livingston at Pittodrie and Hearts away.
Based on the league standings, the Red Army will expect nine points and at the very least a competitive showing against the champions.
Third-placed Well’s run is arguably more difficult.