Complex sentence: He lost 20 of the 23 fights he boxed in after losing the World Bantamweight title to Eddie Martin, though most of his opponents were skilled boxers, if several shades below title contenders.
Split into simpler sentences: He lost 20 of the 23 fights he boxed after losing the World Bantamweight title to Eddie Martin. Though most of his opponents were skilled boxers, they were several shades below title contenders.