Watch Strikeforce World Grand Prix Quarter-Finals: Overeem vs. Werdum for Free: How to Stream the Movie Online at 123Movies. . 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.