Complex sentence: He has spent his professional career playing primarily on the Challenger and Future circuits, although he had the opportunity to play in the 2007 French Open, where he defeated American Sam Querrey in five sets before going down to Novak Djokovic in four sets.
Split into simpler sentences: He has spent his professional career playing primarily on the Challenger and Future circuits. He played in the 2007 French Open, where he defeated Sam Querrey in five sets before losing to Novak Djokovic in four sets.