Every duel between the two greatest footballers of this century is eagerly awaited. For the best part of a decade, they would come around frequently: Messi versus Ronaldo – the rivalry that made Barcelona against Real Madrid extra special. Since Cristiano Ronaldo moved on, to Italy, the serial Ballon D'Or winners have been estranged. They have not shared a pitch for almost two and half years. The chances of their doing so in the first of two 2020/21 Champions League group stage meetings between Ronaldo’s Juventus and Messi’s Barcelona hung on CR7’s being given the green light by Uefa’s health protocols. The Portuguese has been self-isolating, having tested positive for coronavirus during this month’s international break. He is asymptomatic but needed to present a negative test by last night to be included in Juve’s squad. For Messi, captain of a Barcelona <a href="https://www.thenationalnews.com/sport/football/sergio-ramos-penalty-puts-real-madrid-on-way-to-clasico-win-over-barcelona-1.1098851">bruised by defeat</a> to Madrid at the weekend, more significant team news from Turin is that a number of Juve's defenders are unavailable. Centre-back Matthias De Ligt is recovering from shoulder surgery, Alex Sandro nursing a hamstring problem, and there are doubts over whether the totemic Italian central defenders Leo Bonucci and Giorgio Chiellini can shake off muscle injuries. Whoever steps in to a makeshift back line must police Messi, and indeed Ansu Fati, who has five goals from five starts already this season. Ansu only turns 18 on Saturday. Juventus-Barcelona needs neither Messi nor Ronaldo, nor even the rapidly emerging stars of the next generation like Ansu or Juve’s 20-year-old Swedish forward Dejan Kulusevski, to class it as an elite showdown. But neither are in peak form. Though both won their opening group matches comfortably, Juve away at Dynamo Kiev, Barcelona <a href="https://www.thenationalnews.com/sport/football/lionel-messi-breaks-champions-league-record-as-barcelona-go-goal-crazy-in-pictures-1.1096996">by 5-1 against Ferencvaros</a>. Barca have not won in three games in La Liga while Juventus have beaten only one of their first five Serie A opponents – at least on the pitch: they were awarded a 3-0 win over Napoli because their opponents were prevented from travelling to Turin by local health authorities because of a Covid-19 issue. They have a look, as manager Andrea Pirlo put it, of a “team in construction.” Pirlo, 41, is new to the job, and very new to coaching, having been elevated to the head coach at Juve 10 days after the club put him in charge of the youth squad. Maurizio Sarri, who led Juve to their ninth successive Serie A title in July, had been sacked following defeat to Olympique Lyonnais in the last eight of the Champions League. Pirlo found himself promoted with the ink barely dry on his coaching certificates. Because he was such a lauded player, a magisterial midfielder, judgement on his capabilities as a manager will be less rushed than his ascent to the job was. And he will stay cool under pressure; he always was. “I’m not worried,” Pirlo told reporters after Saturday’s 1-1 draw with Verona, when, for the third time on his watch, Juve had to come from behind to gain a point, “Barcelona are a completely different sort of opponent.” A sceptic might point out that this Barcelona, on their third different head coach of 2020 – Ronaldo Koeman – are a completely different sort of opponent to the one Pirlo encountered as a player. Poignantly, his final match in Juventus’s midfield was the 2015 Champions League final: Juventus 1, Barcelona 3. “We’d all love the chance to play that match again,” said Pirlo, “but it’s in the past and there it remains.” That night still haunts the victors. “In 2015 we touched the sky and instead of growing, we declined,” said the Barcelona defender Gerard Pique last week. Pique is suspended for the match but colleagues who shared with them three victorious Champions League campaigns in seven years, like Messi and Sergio Busquets, are impatient to recapture the confidence and drive of that period. Europe has been tough territory for Barcelona since: they were overwhelmed by Juventus in the quarter-finals in 2017, conceded three-goal first leg leads to be knocked out by Roma and then Liverpool in the following seasons, and reached a nadir in August with the 8-2 quarter-final humiliation by Bayern Munich in the quarter-finals. Koeman was appointed within days to replace the sacked Quique Setien. A humbling Juve setback, the loss to Lyon, fast-tracked Pirlo to the top job. Eighty days in, he faces his biggest match yet. “These are the games you want to be involved in,” he said. “We’ll get to see how strong we and Barcelona are.”