The moment he collapsed to the turf, it seemed serious. Making a tackle just 15 minutes into Juventus' Serie A clash with Palermo on Sunday, Claudio Marchisio's knee buckled. He fell in agony, clutching the joint while calling for help from the bench.

His side had already taken the lead when the midfielder was stretchered off and replaced by Mario Lemina, the Old Lady going on to secure a 4-0 triumph that—combined with Napoli's loss to Inter Milan on Saturday evening—opens their lead at the top of the table to nine points with just five games remaining.

Yet despite moving one step closer to what would be a historic fifth consecutive league title for the Bianconeri, Marchisio's health was the immediate concern of coach Massimiliano Allegri after the full-time whistle.

"It's probably the cruciate ligament, we'll have an evaluation tonight or tomorrow," the Juve boss told Mediaset Premium (h/t Football Italia). He went on to say the club hoped those tests would show "it's not that serious," but when Allegri started his post-match press conference, he already knew it was.

"An MRI scan has confirmed that Claudio Marchisio has suffered a ruptured anterior cruciate ligament in his left knee," read a statement on the club's official website. "He will undergo surgery in the next few days."

Out for the rest of the season—and almost certain to miss this summer's UEFA European Football Championship with Italy—it is a desperate loss for all concerned, such is the importance of the 30-year-old to both club and country.

It is the same problem that blighted the Bianconeri in the early part of 2015/16, with Hernanes and Simone Padoin proving to be wholly inadequate replacements as Marchisio missed the first few matches of the campaign.

He returned in October's 0-0 draw with Inter Milan, and Juve's form improved immediately, their record with him in the side making remarkable reading. Indeed, Marchisio has made 32 appearances in all competitions this term, with the Bianconeri registering 25 wins, six draws and just a single defeat in those matches.

The only loss was away to Sevilla in the Champions League, with his tally of zero goals and two assists failing to underline his influence on almost every performance. Fielded in the centre of Allegri's three-man midfield, the team has altered shape around Marchisio, but he remains the key to its success.

According to statistics courtesy of WhoScored.com, his average of 63.5 passes per game leads all Juventus players, connecting on an impressive 88.5 percent of those attempts as he commands the attacking flow of the side.

It is a similar story without the ball, as the same source shows only Paul Pogba (72) and Patrice Evra (51) have made more tackles than Marchisio's tally of 48, while his average of 2.8 interceptions is another team-high mark.

Lemina has blossomed into a fine deputy in recent weeks, but Juventus will be thankful the Serie A title race is no longer as tight as it once was and that so few weeks remain for Napoli to close the gap.

"It's a terrible injury that happened to a serious professional, a treasure of our Juventus," director general Beppe Marotta told RAI Radio 1 (h/t Football Italia) on Monday morning, adding his hope that the player "can return as soon as possible."

That remains to be seen, but the Bianconeri will almost certainly miss the Turin native, a key figure at the centre of everything his hometown club has achieved in recent seasons under both Allegri and his predecessor, Antonio Conte.

With five league games and the Coppa Italia final awaiting, Juventus must find a way to win without Marchisio, something that has proved hugely difficult in the past.