The first warning sign came in the prematch warm-up at the Groupama stadium in Lyon, France. Leonardo Bonucci did not like what he was seeing.

The intensity he expects, particularly on a Champions League night, was missing from Juventus' backups. To his mind, they were too casual, and he didn't hesitate to tell them in front of a crowd of 60,000 fans. When the game kicked off, the Juventus starting XI did not set a much better example. Adrien Rabiot wasted a 3-on-2 on the counterattack and never recovered. Passive defending from Rodrigo Bentancur allowed Karl Toko Ekambi to get in front of him and head an effort against the crossbar. An errant pass from Juan Cuadrado started an attack for Moussa Dembele that, lucky for the Colombia international, ended with the former Fulham and Celtic striker shooting over the bar. A misunderstanding between Miralem Pjanic and Bonucci let Toko Ekambi in again.

Despite several errors, Juventus can attribute the goal they did concede, which sends them back to Turin for the second leg down 1-0 on aggregate in their last-16 clash, down to bad luck. Matthijs de Ligt was off the pitch receiving treatment for a head injury when Lyon made full use of the extra man and scored what turned out to be the winner.

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The Italian side is right to question the referee's decision not to grant Cristiano Ronaldo or Paulo Dybala a penalty in the second half, but truth be told, Juve only have themselves to blame for taking an hour to get the measure of Lyon and find something close to a groove. Extenuating circumstances like Giorgio Chiellini's presence in the stands rather than on the pitch and Pjanic's lack of match fitness in his return from injury only go so far in excusing a first-half performance -- zero shots on goal -- that must rank as the worst of the season.

This had been coming.

Juventus have not played well enough over the past month to inspire confidence that Wednesday's trip to Lyon would be a piece of cake, and even when they have played well this season, the number of one-goal wins (16) mean it has rarely been comfortable.

The team is supposed to peak in February. It's designed that way, in a sense: The medical staff has made more or less everybody available in time, with Merih Demiral the only first-team player not on the short flight across the Alps. New concepts should be assimilated by now, too. Juve fans don't expect to hear embattled coach Maurizio Sarri say: "I'm having difficulty getting the idea across to the team that they need to pass the ball quickly." That will wash in August and September. It won't at this stage of the campaign.

So much more was expected of Sarri when he was appointed manager last summer. The fans, used to dominating Serie A, could appreciate that he needed time. The team is transitioning to a style diametrically opposed to the one it has played over the past five years. But here's the thing: Juventus have lost a lot of the qualities associated with them under Massimiliano Allegri without gaining many of the ones that spring to mind when we think about Sarri.

Recently, Sarri has suggested that opinions of Juventus' performances would be different if they'd been a little luckier in front of goal. They struck the woodwork a total of seven times against SPAL, Brescia and Verona combined, but reflecting on those chances, a couple of things stand out. They are either moments of individual brilliance from Ronaldo and Dybala, or they come from set pieces. They are not missing the final touch following fluent patterns of play or truly cohesive football.

Sarri has explained underwhelming league displays away as being a consequence of his players finding it hard to get up for Serie A games, particularly against the smaller teams, having won the Scudetto unchallenged for almost a decade. Aside from the Derby d'Italia in October, Juve's best performances for the most part have been reserved for the Champions League, where they qualified top of their group with two games to spare for the first time in their history. Sarri put that down to the players caring more about it and raising their game accordingly.

So what happened in Lyon, then? And how come it followed the trend of recent weeks? It would suggest this isn't a simple a case of whether the players fancy it or not. It goes deeper than that.

The defence is porous by Juventus standards. They haven't kept a clean sheet on the road in almost three months and have won just one of their past five away games. Letting in the odd extra goal would be acceptable if the attack was firing on all cylinders; instead, it ranks fourth in the league and is Ronaldo-dependent.

All is not lost, though. Juventus are still top of the league, one point above Lazio (and two above Inter) with 13 games left. The second leg of their Coppa Italia semifinal next Wednesday -- stream live in the U.S. on ESPN+, 2:30 p.m. ET -- is at home in the Allianz Stadium, and Milan will be without the suspended Zlatan Ibrahimovic and Theo Hernandez, their two best players. Coming back against Atletico this time last year also represented a much more daunting task than overturning a one-goal defeat against a Lyon side that would be 11th in Ligue 1 were it not for the better goal difference they enjoy over Reims, Montpellier, Nice and Nantes.

That said, Sunday's Derby d'Italia -- stream live on ESPN+, 2:35 p.m. ET (U.S. only) -- with Inter keeps the pressure on. Losing to Antonio Conte on his return to Turin would further complicate life, and job security, for Sarri. Earlier this week, Juventus president Andrea Agnelli said the club is happy with its new manager, and the three-year contract he was given in the summer showed an appreciation that it would take a long time for "Sarrismo" to take hold of the Old Lady. The environment around the club, however, is more restless than rational, and Sarri faces two challenges: improving performances and keeping a skeptical fan base on his side.