From his hoody and his team selection right through his inability to stir City into life from the bench, this was as lethargic as things have been for City under the Chilean.
The former striker, on his first trip back to the club where he was a folk hero, was the romantic tale this weekend. The City fan knew there would be a sting in it for his team. However, this was not the fates conspiring against City; one of those inexpicable matches in which all reason and sense are discarded.
This was a result forged, initially, in the approach of the two managers and then in the tasks executed by their players. Night and day in that respect. Resplendent in his match-day suit, Rosler shouted himself hoarse, bending, squatting, patrolling the touchline, up and down, up and down, like a tiger in a cage, ensuring his players followed his instructions to the letter. At one stage in the first half, he was telling them what passes to play.
"Our worst half of the year," instead, was Pellegrini's assessment. "We didn't have the pace to play against a team in a very good moment." With his shaggy mane and hooded tracksuit, the Chilean cut an apathetic figure.
"Maybe we thought it was not so difficult [before the game]," he said. And maybe, in the end, it wasn't as difficult as Uwe Rosler thought. Pellegrini was impassive after the first Wigan goal. He altered nothing as time and again, in possession, Wigan picked the right pass and starved City of the ball in meaningful places.
When the changes came, they came desperately. He rolled three dice hoping to see two sixes among them. While the introduction of James Milner drew a better display from the right back Micah Richards, Edin Dzeko and David Silva were less effective. The Bosnian hit the post with one header and saw another, for a potential equalizer, flash wide. City did not deserve it. The scarcely deserved the one they did score, opined Rosler. Joleon Lescott "clearly offside" and interfering with play.
Silva put the ball under his foot and tried to pass it well when he came in, but the frenetic nature of City's late strategy also featured Lescott and, latterly, Costel Pantilimon up front, illustrating a muddled approach.
Questions will have to be answered about the caliber of replacements for Vincent Kompany. It made sense to rest the Belgian with Barcelona on the horizon and an international match behind him. Nonetheless, City can not defend in his absence. Richards was posted missing as Marc-Antonie Fortune ghosted down the right flank in the first half and Martin Demichelis was turned inside out before conceding the penalty.
For the second goal, Richards had his hands behind his back in the box as James McArthur crossed along the ground for James Perch's tap in while Lescott let the ball go past.
Even that goal showed the contrast in hunger between the sides. Gael Clichy was favorite for the ball, but the former Newcastle United man simply showed more desire to get there. At the other end, Emmerson Boyce, as loyal a servant as they come, somehow diverted the ball over the bar from right in front of the goalline as Dzeko lurked. Even on replays, it defies logic that he kept it out. But keep it out the Wigan captain did and in the cup he kept his side. "You need match winners at both ends," said Rosler, whose side has now endured 52 matches this season. "That tackle has shown desire and willpower. I can only take my hat off to my players."
Boyce's opposite number, Yaya Toure, flounced down the tunnel after being substituted. He was lucky not to be sent off for two petulant fouls. His body language was all wrong throughout. It was symptomatic of City's display on the day. He threw his arms around in frustration that Wigan seemed to want it more than they did. How dare they come to the Etihad and try this hard. Don't they know the script?
All season long Pellegrini has parried enquiries about a potential quadruple. His side has the Capital One Cup in the bag, but that is very much the bottle of champagne handed out when you win the National Lottery. No one really cares.
Since the start of 2014 he has watched his side surrender its grip on the Premier League trophy to Chelsea, its Champions League credentials to Barcelona and now its FA Cup dreams to Wigan.
The Latics now edge towards unlikely successive FA Cup wins. That's six consecutive wins for the Latics now since defeat at Huddersfield in February and five of those have been away from home. This isn't the stuff of dreams. This was what they came for.
Both teams believed they could do it; only one followed through.