Mandzukic danger for Barca - How super, selfless Mario can outshine Messi and co
Barcelona's weakness on the right of defence means Juventus forward Mario Mandzukic could prove as important as more celebrated team-mates.
Slight, skilful, pacy and inventive attackers have proved a key ingredient in Barcelona becoming the Champions League's defining side during the modern era – winning four titles in the past 11 seasons.
On Tuesday, their hopes of another could be severely damaged by a forward who is not readily associated with any of those virtues.
During Croatia's illuminating and all-too-brief appearance at Euro 2016, Mario Mandzukic was a lumpen presence as the focal point for Luka Modric, Ivan Rakitic, Ivan Perisic and Marcelo Brozovic – a midfield line-up that showed razor-sharp brains and silken feet working in tandem before a torpid extra-time exit against eventual winners Portugal in the last-16.
Mandzukic failed to score in three matches despite such high-class prompting and, having turned 30, the former Bayern Munich and Atletico Madrid striker looked ready to fall in as Gonzalo Higuain's understudy at Juventus before playing out the later days of his career with less illustrious employers.
However, with the help of Massimilliano Allegri's ever-impressive tactical flexibility, Mandzukic has been allowed to reinvent himself from archetypal number nine to consummate team-mate, filling an unlikely role that places him in prime position to hurt Barcelona's flimsy rearguard in Turin.
A back-to-goal, aerially dominant centre-forward, there is still cause to blink in disbelief and scratch your head when Mandzukic lines up on the left-wing for Juventus, with the prodigious Paulo Dybala inside him at number 10 and Higuain primed to pilfer prolifically.
Seven goals and five assists across all competitions this season is not a return worthy of shouting from the rooftops, but Mandzukic has assumed increased importance since Allegri's switch predominantly to a 4-2-3-1 formation in January.
Set against most right-backs, his physical advantages are an obvious plus. The way Mandzukic obliterated Lazio's Patric in the air to set up Dybala's sublime opener after four minutes in January's Serie A game – the first that Juve's main three forwards started together - offers a vivid demonstration of how Barca might be brought down.
Since Allegri's tweak, Mandzukic has made (18) and won (11) more tackles than each of Higuain and Dybala, matching the latter on 15 interceptions despite playing four fewer games.
He has also won more duels than both and his major strength has been highlighted rather than sidelined on the left flank. His 75 aerial challenges over recent weeks outstrip 29 between Higuain and Dybala; Mandzukic has won 58 compared to their collective nine.
Allegri confirmed on Monday that Higuain, Dybala and Mandzukic along with winger Juan Cuadrado, would all start against Barca, leaving Luis Enrique with plenty to ponder.
Since their humiliating 4-0 first-leg loss to Paris Saint-Germain in the last-16, Barcelona have won eight of their subsequent 10 matches.
But alongside the seismic, historic comeback to send PSG packing, there are away LaLiga defeats to Deportivo La Coruna and Malaga, and just two clean sheets during this period.
The right side of defence is a particular problem. Dani Alves has not become the influential figure at Juventus that he was at Barcelona, but the void from when he left Camp Nou last year still yawns.
Sergi Roberto scored the unforgettable decider to sink PSG and counters fears La Masia's well has run dry, but the suspicion remains he might be better deployed as a midfielder.
Luis Enrique solved his right-back problem by simply not picking one against PSG, but knee surgery means Rafinha is no longer an option as an attacking wing-back.
Javier Mascherano filled in on the right of a back four at Malaga, although Jeremy Mathieu's one-man variety act in that game means the Argentine is more likely to revert to centre-half, whether in a two or a three.
Whatever Luis Enrique's decision, a tireless and focused Mandzukic represents a clear and present danger. Lionel Messi, Luis Suarez, Neymar, Higuain and Dybala promise a feast of attacking brilliance between them during this mouth-watering quarter-final, but it might just be a more unheralded forward who holds the key.