An underwhelming start to the Serie A season has left Juventus just four points above the relegation zone and nine points behind leaders Fiorentina after eight games.
But in true Jekyll and Hide style, Juve - last season's beaten finalists - appear to transform when the challenge of Europe's premier club competition looms.
They are among only six teams with maximum points from their first two games, following a 2-1 win at Manchester City with a 2-0 defeat of Sevilla that has propelled them to the top of a tricky Group D.
Holding a three-point cushion on both City and Sevilla, Juve will take a significant step towards the knockout stages with victory over Andre Schubert's improving Bundesliga side on Wednesday.
Observers looking at Juve's Serie A performances and position should be wary.
On Sunday, the Bianconeri snatched a point from a pulsating scoreless draw away to on-form Inter Milan, but it was a compelling display from the champions and, with the exception of a poor first-half display from Paul Pogba, dispelled any existing doubts about Juve's steadily-improving form.
After the game, Allegri alluded to Juve's split personalities in a post on Twitter, writing "We played a good game, now let us see #euroJuve and get focused on the Champions League."
The statistics back up the 48-year-old coach.
Juve stunned City at the Etihad Stadium just after they had suffered defeats to Udinese and Roma, and could only draw with Chievo at home, in their first three games of the season.
Since then, Juve have only slowly improved on the domestic front. But Allegri has welcomed back key players from injury, including midfielders Sami Khedira and Claudio Marchisio as well as experienced defender Andrea Barzagli.
Although Juve are not quite the side that Argentinian striker Carlos Tevez inspired to a league and Cup double last season, the Bianconeri are finally beginning to play like a team.
"Now, I have all of the squad available for selection, even if some of the lads are lacking a little match fitness," Allegri said.
Allegri is expected to deploy his preferred 4-3-1-2 formation for Wednesday's clash in Turin, with Alvaro Morata already sure to claim one of the two strikers' spots.
The Spanish international's goal against Sevilla last time out meant he equalled Alessandro Del Piero's club record of scoring in five consecutive Champions League games.
Mario Mandzukic and Paulo Dybala are vying to join him up front.
Gladbach have also endured a Jekyll and Hyde season so far, in the Bundesliga at least.
The Germans suffered five straight league defeats and lost 3-0 to Sevilla in Europe, leaving them bottom of Germany's top flight and prompting coach Lucien Favre's shock resignation in mid-September after four successful years at the helm.
Schubert was installed only as caretaker coach, but the change was immediate. The Foals went on to win four league games on the trot and although a 2-1 defeat to City has left them bottom of the group without a point, the Germans are defiant.
"There is a jolt going through the team and the way we are playing at the moment is sensational," defender Tony Jantschke said after Gladbach hammered Eintracht Frankfurt 5-1 away on Saturday.
"The fact is that we are not exactly playing with our heads down at the moment.
"We are going to Turin to win, we want to show that we can compete against the big names."
Fleet-footed winger Patrick Herrmann is out with a knee injury while while Swiss defensive midfielder Granit Xhaka is doubtful with an ankle knock.