Complex sentence: However, on 13 August 2013, he suffered a tear to his left Achilles tendon on just the second day of training camp and was subsequently ruled out for the entire 2013--14 season.
Split into simpler sentences: However, on 13 August 2013, he suffered a tear to his left Achilles tendon during the second official training session of the team's pre-season schedule. He was subsequently ruled out for the entire 2013--14 season.