Complex sentence: In March 2015, the Dolphins made the biggest free agent signing of the NFL off-season; they signed defensive tackle Ndamukong Suh to the richest contract in NFL history for any defensive player.
Split into simpler sentences: In March 2015, the Dolphins made the biggest free agent signing of the NFL offseason. They signed defensive tackle Ndamukong Suh to the richest contract in NFL history for any defensive player.