Complex sentence: Limping in the final set, many people thought his season was over, however a strong summer saw Nadal win Montreal, Cincinnati, and then the U.S. Open (def. Djokovic), thus clinching the Emirates Airlines U.S. Open Series.
Split into simpler sentences: Limping in the final set, many people thought his season was over. But a strong summer saw Nadal win Montreal, Cincinnati, and then the U.S. Open (def. Djokovic), thus clinching the Emirates Airlines U.S. Open Series.