Watch Strikeforce World Grand Prix Quarter-Finals: Overeem vs. Werdum (2011) : Full Movie Online Free Strikeforce World Grand Prix Quarter-Finals: Overeem vs. Werdum, also known as Strikeforce: Dallas, was a mixed martial arts event held by Strikeforce. The event took place on June 18, 2011 at the American Airlines Center in Dallas, Texas. The main card aired on Showtime while the preliminary card aired on HDNet.