Valdes injured himself making a save. He made an initial jump and the a second "hop," before falling to the turf and immediately calling for the medical staff. Video showed that his knee did have a twist, though it is unclear exactly where the injury occurred. Valdes did have a previous injury to his calf, back in a November friendly. It's impossible to say whether they were related in any way.
In Europe, a "cruciate tear" is common parlance for a sprained ACL. The time frame would indicate that Valdes will need surgery, which could take him six to twelve months to recover from. Since a goalkeeper doesn't have to run as much, many assume it would be on the short end for recovery, but even the method of his injury reminds us that a keeper has to be very athletic, moving side to side and jumping.
While initial reports stated Valdes would miss six months, the normal recovery period can range from six to twelve months. There is significant variance based on whether there is other associated damage inside the knee, including other ligaments, cartilage and meniscus. The rehab can also vary due to many factors. Comparisons across sports are difficult to make and since this is not a common injury to goalkeepers, it's difficult to get to a more solid number until Valdes is actually in the process.
There is no reason to think that Valdes will not be able to return. Physically, almost all players return from this type of surgery and get back to a similar level. The loss of time is tough, but Valdes is not a player that is overreliant on physical gifts anyway.
Valdes is not only out for the remainder of the Barca season and cups, but is very unlikely to be available for the World Cup. While Spain has solid options in Iker Casillas and Pepe Reina, this may be a weak spot for the reigning champs. Casillas has been supplanted in goal at Real Madrid and Reina has had mixed reviews at Napoli. The likely replacement on the squad is David De Gea from Manchester United.
This is the second such injury to a major club's goalkeeper in the last month. Napoli's Rafael had an ACL sprain that will keep him out until next season as well, during a game in late February. Rafael was Reina's backup, in an odd tie-in. While this is not a common injury, the athletic demands on a goalkeeper are increasing, meaning we could see a rise in this type of injury.
Barcelona is coming off a big win in El Clasico that keeps them within range for the La Liga title, fighting with not only Real Madrid but Atletico Madrid as well, led by their young keeper Thibault Courtois. Courtois is on loan from Chelsea and is the target of many clubs since Chelsea is set with Petr Cech in goal.
In addition to league play, Barca still has the Copa Del Rey Final in a few weeks, plus Champions League play that starts on April 1. The club will be matched against Atletico Madrid, which could make it even more challenging for both clubs.
With Valdes out, Barca will turn to Jose Manuel Pinto. Pinto has been a backup since coming to Barca in 2008 and wasn't considered to be in line to take over when Valdes leaves. Unlike Real Madrid last season when Iker Casillas was injured, Barca won't be able to go out and get a transfer or loan.
Pinto has seen plenty of play in Cup play, so he won't be overmatched. Behind Pinto will be Oier Olazabal, a Barca youth product who is generally untested in high level play, having made only one league appearance for the first club.
Valdes is likely to be leaving Barca at the end of the season anyway. Many believe that Barca is already scouting replacements and that Valdes will have several suitors, including big clubs like AS Monaco, Manchester City and Liverpool. Barca has been connected with several possible replacements, including Reina, Courtois and Tata's former keeper in Argentina, Nahuel Guzman.
Both Valdes and his club will have challenges in dealing with this injury, but in very different ways. Barca will have to make it through the league and cup schedule this year with their backup keeper while Valdes will have to convince his next club that he's still as valuable.