Tito Vilanova's side are already without captain and central defender Carles Puyol for eight weeks after he dislocated an elbow in the win over Benfica, while fellow centre-back Gerard Pique has yet to return from an ankle injury.
Now Brazil international Alves will miss at least the first match against Celtic at the Nou Camp on October 23 after being ruled out for three weeks.
Real Madrid's Cristiano Ronaldo was also in the wars – and on the scoresheet – as he suffered a damaged shoulder in the first Clasico of the season.
He matched Lionel Messi blow for blow as each superstar bagged two goals apiece in an entertaining draw.
Barca headed into the game eight points clear of their arch rivals and boasting a 100% record from their first six matches, but found themselves trailing midway through the first half when Ronaldo netted for the sixth straight Clasico.
But Messi equalised with a scrappy goal soon after and then put the hosts ahead with a stunning free-kick on the hour, only for Ronaldo to capitalise on sloppy defending midway through the second half to ensure honours ended even.
Substitute defender Martin Montoya was almost an unlikely match-winner for Barca on 88 minutes but his right-footed attempt from the edge of the box crashed back off the bar.
"We were superior at times but it was a very even game," Barca midfielder Sergio Busquets said.
"Everything is the way it was but with one match less," added the Spain international.
Real manager Jose Mourinho said: "The result is perfectly suited to the match, which was very good and which the whole world enjoyed, just like myself and the players from both teams.
"I prefer to focus on that because it's the true reflection of the game, well contested and without knowing until the last moment who was going to win," the Portuguese added.
"The league is how it was, my team pleased me a great deal and the world is happy."