Complex sentence: Yardbarker was founded in March 2006 by Jack and Jeff Kloster, Pete Vlastelica and Mark Johns as a site that enabled sports fans to write and discuss sports with other fans, bloggers, and professional athletes.
Split into simpler sentences: Yardbarker was founded in March 2006 by Jack and Jeff Kloster, Pete Vlastelica and Mark Johns. The original site enabled sports fans to write and discuss sports with other fans and bloggers, as well as professional athletes.