Complex sentence: Willis was a member of two World Series champions: the Tigers in the 1984 World Series and the Twins in the 1991 World Series, however, he did not get a ring in the 1984 Series because he was traded around the middle of the season.
Split into simpler sentences: Willis was a member of two World Series champions: the Tigers in the 1984 World Series and the Twins in the 1991 World Series. However, he did not get a World Series ring in the 1984 Series because he was traded around the middle of the season.