Carles Puyol's dislocated elbow will keep him out of action for about two months, and will mean Barcelona coach Tito Vilanova faces another unwelcome defensive conundrum for Sunday's La Liga 'Clasico' at home to Real Madrid.
In his first game back after a knee injury, Puyol landed heavily in the second half of Tuesday's 2-0 Champions League Group G victory at Benfica and the La Liga club said on Wednesday he would be sidelined for about eight weeks.
The shaggy-haired 34-year-old, whose regular central defensive partner Gerard Pique has not played since hurting his foot two weeks ago, was taken to hospital for checks before flying back to the Catalan capital.
He spent the night under observation in a clinic and appeared in good spirits on Wednesday morning.
"Good day! The sun always comes out again... thanks for all your messages! A big hug," he wrote on his Twitter feed.
Barca will sorely miss Puyol's experience and inspirational do-or-die attitude on Sunday, and if Pique does not recover in time, Vilanova may again be forced to deploy new signing Alex Song alongside fellow converted midfielder Javier Mascherano.
Neither were convincing in Barca's 3-2 win at Sevilla over the weekend, and Song has yet to settle properly after joining from Arsenal in the close season.
Vilanova also has the option of throwing youth academy graduates Marc Bartra or Andreu Fontas into the fray, although it would be a major gamble given the importance of the game.
Victory for Barca, who have won all six of their La Liga games and top the standings by two points from Atletico Madrid, would put them 11 points clear of their bitter rivals.
Jose Mourinho's Real Madrid side, who play at Ajax Amsterdam in Champions League Group D later on Wednesday, have already lost twice in La Liga, the same number of defeats as in the whole of their title-winning campaign last season.
"I have always said it, we have always had problems in central defence but we will get through it," Vilanova told a news conference after the Benfica match.
"It's not just a question of what Barca loses for the Clasico on Sunday but also what it loses in terms of all the other matches," he added.
Barca had been forced to "convert players into positions which are not theirs", he said, but could potentially count on "homegrown players, which is what we have them for".
Puyol's injury took some of the shine off yet another victory for Vilanova's men, who have won all eight of their matches in La Liga and the Champions League this season.
Real did get the better of Barcelona in the Spanish Super Cup, winning the second leg of the traditional season-opener at the Bernabeu stadium 2-1 to level the tie at 4-4 and take the trophy on the away goals rule.
There was at least some good news for Vilanova on Tuesday, with Andres Iniesta back to fitness after returning from Spain duty last month with a muscle strain. The World Cup winner came on in place of Cesc Fabregas for the final 20 minutes of Tuesday's game.
Forward David Villa, who is gradually coming back from a broken leg sustained in December and came off the bench to score the winner at Sevilla, replaced Pedro with about 10 minutes left and looks to be back to something close to his best.
