Barcelona will be without forward Alexis Sanchez for approximately a month after he picked up an injury on international duty. During a friendly with the Chilean national team, Sanchez went down in pain and had to leave his team's match against Serbia after just 20 minutes of play. Luckily, his injury was just a sprain, but the damage done to his ligaments will cause him to miss out on around four weeks of action.
While Sanchez is still arguably first choice at Barcelona, he's had a rough time so far this season. He's yet to score a goal, and his shaky form has caused Christian Tello and David Villa to pick up more playing time. While Barcelona will certainly miss him, they have a few other capable and able-bodied forwards, even with Isaac Cuenca out injured as well.
Between La Liga, the Champions League and Copa del Rey, Sanchez will miss approximately eight games during his recovery.