This paper examines how professional female tennisplayers react to: i) prize incentives and ii) heterogeneity in ex ante players' abilities. It is found that a larger prize spread encourages women to increase effort, even when controlling for many tournament and player characteristics. Further results indicate that uneven contests lead favourites to win more games and underdogs to be less performing. They also show that the performance differential between players increases with the ranking differential. These findings suggest that the outcome of a match is more linked to players' abilities than to players' incentives to adjust effort according to success chances.