But the Swans boss believes his team can also measure themselves against one of the game’s top modern coaches when Forest visit the Swansea.com Stadium in the third round of the Carabao Cup.
Postecoglou was a divisive choice as a successor to Nuno Espirito Santo when Forest owner Evangelos Marinakis decided to sack the manager who guided the club into Europe last season.
The Australian began his spell with a 3-0 defeat at Arsenal last weekend and now faces the pressure of an away trip to Championship opposition.
But Sheehan, whose side are unbeaten at home this season, struck a respectful tone when asked about Postecoglou, the recently appointed Forest boss whose track record at Celtic and Tottenham convinced the Premier League club to hand him the job.
“He’s top. Look, he’s a top-class manager and obviously I’ve seen his teams play, my staff have seen his teams play,” Sheehan said.
“He won a trophy at Spurs and he knows how to win — it’s a good habit to be involved in.
“At Celtic, it was the very same. He’s a manager who has been there and done it. So, it’s a good test for me, obviously, to come up against somebody with that level of experience.”
Sheehan said he expects Forest to carry the hallmarks of Postecoglou’s attack-minded approach, even though the Aussie has only just stepped into the role at the City Ground.
“I think they’re a high-tempo team, they want to control the ball, they want to attack fast at the right moments.
“They overload a lot of areas on the pitch. I think they’ve got many rotations
within their team,” he explained.
“He’s got a clear way of playing. You can see it at Celtic and Spurs, and I think there is a clear identity he’ll want to put in place as quickly as possible.”
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The challenge for Sheehan is compounded by a compact schedule. Wednesday’s 8pm kick-off leaves just over 60 hours before Swansea return to Championship duty at Birmingham on Saturday lunchtime.
Squad rotation is therefore unavoidable, with fringe players and new signings set for an opportunity to impress.
Striker Adam Idah, signed from Celtic for £6m, could be handed his first start.
On loan recruits Ishe Samuels-Smith and Manuel Benson could also make their first full appearances for the club.
Both Chelsea defender Samuels-Smith and Burnley winger Benson were unused substitutes in the weekend 2-2 draw against Hull, where Sheehan’s side surrendered a goal deep into stoppage time.
“Yeah, it could be Adam,” Sheehan admitted.
“That’s what you want, isn’t it, - breeding competition within the squad. We want to have that competitive environment, individual specific positions all over the pitch. Everybody driving each other, even in training. That’s how we get better.”
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Swansea have already seen off two rounds to get here, and Sheehan is eager to ensure the journey continues despite the step up in class.
While acknowledging Forest’s resources, he insisted his team will not sit back.
“We want to go and be the best versions of ourselves again,” he said.
“It’s a very competitive game, a cup game, and we’ve won two games to get here so, yeah, we want to win three in the cup.
“The best way to respect these teams is to go up against them and see how far we are away.”
“Any player who plays in the Premier League, you won’t hear me downplaying it because it’s the toughest league, potentially, in the world.
“You’ve got to be highly physical, highly technical, tactically very strong and mentally incredibly strong. Any team they put out will be a difficult test for us.”
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While Wednesday’s tie offers the chance to test themselves against elite opposition, Sheehan was also upbeat about Swansea’s long-term ambitions.
He points to Forest’s recent journey — promotion, survival, and now European football — as an example of what the Swans might aspire to emulate.
“For any team to come up from the Championship and sustain their stature in the Premier League, that’s obviously the aim.
“First of all, get there, then you stay there. For us, ultimately, we’re trying to build to get to that top cohort of clubs in the Championship, first of all.
“Whether it’s this year, whether it’s next year, whenever it is, we want to keep building and closing that gap.”