Complex sentence: On 11 September 2008 Sykes signed a contract with the Yamaha Motor Italia World Superbike team for the 2009 season, with an option to extend that contract until 2010 depending on results.
Split into simpler sentences: On 11 September 2008 Sykes signed a contract with the Yamaha Motor Italia World Superbike team for the 2009 season. With an option to extend that contract until 2010 depending on results.