Not talking about the 1-day sparring between two ranked fighters. But the sparring partner, who work with the Top Dog for some time, then came back to beat his Bossman in a legit fight. Larry Holmes (vs Ali) would be a good example.
WALCOTT LOST, but many thought he won: Jersey Joe Walcott’s two Heavyweight Championship title fights with champion Joe Louis signaled the end of an era. Joe Louis had reined supreme through the 1930s and 40s, but by 1947 his career was winding down. On December 5, 1947 Louis was challenged by Jersey Joe Walcott, an ex-sparring partner and fellow veteran heavyweight with a mixed record. Louis was the confident favorite, but Walcott was in top form. Jersey Joe’s power and craftsmanship surprised Louis, who was knocked down twice in the fight. Unable to cope with Walcott’s speed and counterpunching, Louis appeared to loose after 15 rounds, but sadly for Walcott, the sentimental judges awarded Louis a controversial split decision.
James J. Jeffries was a sparring partner for James J. Corbett. In 1900 and 1903 champion Jeffries turned back the title challenges of former champion Corbett.
Not exactly his sparring partner as such but his trainer and boss, Archie Moore against the young upstart cassius clay.
