Why Sergi Roberto & Andreas Christensen aren't playing in Barcelona vs PSG

When Xavi turned to Andreas Christensen with 15 minutes remaining of the first leg of their Champions League quarter-final tie against Paris Saint-Germain, preservation was the priority.

Having started his first game in over a month, Frenkie de Jong was unable to go the distance. The scoreline, meanwhile, read two apiece; a fine result away from home in Barcelona's books.

Instead, it was substitute Christensen who proved decisive. While Raphinha was understandably lauded the protagonist of the evening, Christensen was the match-winner as he nodded home from a corner almost immediately after his introduction, ensuring Barcelona took a 3-2 cushion back home.

Barca will take a one-goal advantage into Tuesday's second leg on home soil, but Xavi won't be able to call upon Christensen for further heroics. Here's why.

The former Chelsea defender picked up a booking two minutes from time last Wednesday to stop PSG youngster Warren Zaire-Emery from breaking away on the counter.

It was Christensen's third booking of the Champions League campaign and he earned a one-game suspension as a result.

He's not the only Barca star suspended for the second leg either. Sergi Roberto, perhaps a surprise inclusion in Xavi's XI last week, picked up a first-half booking which was also his third of the campaign.

Three bookings warrant a one-game suspension, with the slate being wiped clean after the quarter-finals to prevent players missing the final as a result of yellow card accumulation. Thus, the two players will be available for the first leg of the semi-final should Barcelona advance.

While not a natural holding midfielder, Christensen has helped provide Barcelona's midfield with stability since his conversion and his absence could be