Complex sentence: During the first rounds, Trout seemed to have a good game plan; however, after the third round, it was Alvarez's power that took over, eventually scoring a knockdown on the seventh round to give Trout the first knockdown of his career.
Split into simpler sentences: During the first rounds, Trout seemed to have a good game plan. However, Alvarez's power took over after the third round, eventually scoring a knockdown in the seventh round to give Trout the first knockdown of his career.