ESPN has launched "Invisible Players," a thought-provoking campaign that highlights the way we too often think of sports as a male domain.

Created out of Sao Paulo agency Africa to promote ESPN Brazil's new women's sports portal ESPNW, the effort invited avid sports fans to test their knowledge. They watched key points scored in a variety of real games including soccer and basketball, and were asked to identify the star athlete who made the winning moves. The replays were filtered in a way that obscured the identities of the athletes.

Fans identified big soccer goals as being made by football stars such as Messi and Neymar. They attributed impressive dunks and baskets to Michael Jordan, Kobe Bryant and LeBron James, and they said the likes Kelly Slater, Gabriel Medina and Adriano "Mineirinho" de Souza were behind the breathtaking surfing performances.

Turns out, they were all wrong. In each case, a female athlete -- WNBA star Maya Moore, pro-footballer Marta Vieira, and big wave champ Maya Gabeira -- pulled off the stunning moves.

Interviewed afterward, fans said things like "I never thought it could be a woman," and "When you think about athletes, you think about men."

The video ends with the message: You might know sports. But if you didn't get the answers right, you need to learn more about the power of women.

For another film that sets out to tackle our gender biases, check out MullenLowe's work for educational charity Inspiring the Future.