Athletes display a variety of emotions after a win or a loss. It can be difficult to distinguish between happiness, sadness or surprise, especially if they are subtle facial expressions of emotions.
It is also important to note that still pictures such as these are hard to judge, as they only represent a fraction in time and emotions can come on and off the face in a matter of seconds. Keep in mind that it is also often hard to judge a picture like this without knowing the context in which it was taken (e.g. what may have happened the moment before this was taken)
You might notice that each player is displaying a different facial expression. The Baugranas as they are called enjoyed their 4-0 victory, which they dedicated to their coach Tito Vilanova. However, what is not obvious is that despite the happy news of their undefeated record the players are dealing with the hospitalization of their beloved coach (Vilanova).