Of all the players in the Juventus squad, Blaise Matuidi is arguably the hardest to replace.
No other player in the Turin side quite matches the Frenchman's combination of expert tackling, commitment, boundless energy, tactical awareness and eye for goal.
The 30-year-old's signing from Paris St Germain in August was initially given a lukewarm reception by Juventus fans hoping for a more glamorous addition to the squad but he quickly won them over.
He is the closest thing to Arturo Vidal since the Chilean, hugely popular with the Juventus supporters, left for Bayern two years earlier.
Matuidi has been a key player in the tactical switch which has revived Juve's season, plugging the defensive holes which had threatened to undermine their bid for a seventh successive Serie A title.
After a 3-2 defeat at Sampdoria in November, when Matuidi started on the bench, coach Massimiliano Allegri decided that his team strengthening defensively and changed the 4-2-3-1 formation for a 4-3-3.
Apart from Friday's 2-0 win at Fiorentina, Matuidi has started in every Serie A game since then and Juve have notched 10 wins and a draw in 11 outings, conceding only one goal in the process.
But Matuidi has been ruled out of Tuesday's Champions League round of 16 first leg tie at home to Tottenhan Hotspur after suffering a thigh injury in the 7-0 win over Sassuolo on Feb 4, leaving coach Allegri to mull other options.
Claudio Marchisio stepped into the rule in Friday's win over Fiorentina, completing a three-man field alongside Miralem Pjanic and Sami Khedira, although, after a series of injuries, he seemed to run out of gas in the second half.
Another option for Allegri is 20-year-old Rodrigo Bentancur, who has started five Serie A games since he was signed from Boca Juniors in July and offers physical strength even if he lacks Matuidi's all-round ability.
Stefano Sturaro is another possible choice.
Allegri also has to find a replacement for playmaker Paulo Dybala who is not expected to have recovered from a hamstring injury, although that role is widely expected to go to Brazilian Douglas Costa.
Alternatively he could switch back to the 4-4-2 with Costa and Federico Bernardeschi on the wings and Gonzalo Higuain and Mario Mandzukic at the two forwards.
Allegri is a pragmatic coach and another change cannot be ruled out.
"This is a different Juventus to previous seasons," he said recently.
"We started out with one tactical system, now we use another and I think we’ll change again going forward, because we could use more players with certain characteristics."
"There’s no secret to our success -- we simply have lads with good values and who want to win," he added.
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