Despite the increasing use of social media among personalities such as politicians, athletes, and entertainment celebrities, little is known about the intensity of competition that these pop- ular users engage in to draw the attention of other users, and how their competition affects the users’ engagement with social networks. In this research we propose a model where social media users supply content in return for user attention. Using Twitter data on soccer players from the National Women’s Soccer League (NWSL), we estimate a demand model where users decide how to allocate their attention among players, based on their content posted on social media and their performance on the soccer field. We consider the amount of tweets mentioning a player’s account as a measure for the level of attention captured by the player. On the supply side, players decide the amount of social media content posted on the platform. We show that the attention substitution between players depends on their posting activity and soccer perfor- mance, but also on personal characteristics, such as physical attractiveness and team affiliation. Our analysis suggests that the competitive pressure to capture user attention is responsible for about one out of three tweets posted by players. This additional content benefits the so- cial network, increasing by 7% the users’ activity on the platform. We also quantify the effect on user activity of a revenue-sharing model in which Twitter rewards players for posting tweets.