Complex sentence: He chose Cena, stating that if Barrett won the match and the WWE Title, Cena would be allowed to leave the Nexus; however if Barrett failed to win the title, Cena would be fired.
Split into simpler sentences: He chose Cena, stating that if Barrett won the match and the WWE Title, Cena would be allowed to leave the Nexus. But if Barrett didn't win the title, Cena would be fired.