The event, Strikeforce: Shamrock vs. Diaz will mark the promotions debut on Showtime and it's first step towards becoming a major player on the MMA promotional scene. To that end the company seems to be pulling out all the stops, putting together a high profile main event between former UFC stars Frank Shamrock and Nick Diaz.

Now sources have informed Fightline.com that Josh Thomson will battle Gilbert Melendez on the card as well.

Thomson (16-2) defeated Melendez in their first encounter last summer via lopsided unanimous decision to take the Strikeforce world lightweight championship. He then defended the title three months later, earning a first round knockout against Ashe Bowman.

Melendez (14-2), who hasn't fought since his defeat, will now have the unusual opportunity to jump right back in against an opponent who just defeated him.

Below is a look at the current rumored participants and match-ups for the April 11 card:

- Nick Diaz vs. Frank Shamrock

- Josh Thomson vs. Gilbert Melendez

- Joe Riggs vs. Jake Shields

- Benji Radach vs. Scott Smith

- Cristiane "Cyborg" Santos vs. TBA