Complex sentence: Wathan was hired as manager for the Royals late in the 1987 season, in which he managed five seasons there, having two winning seasons in 1988 and 1989, finishing second in the American League Western Division both times.
Split into simpler sentences: Wathan was hired as manager for the Royals late in the 1987 season. He managed five seasons in Kansas City, having two winning seasons in 1988 and 1989 and finishing second in the American League Western Division both times.