I actually don't think this is that uncommon. The following fighter's legacies were enhanced because of who they lost to and the courage and skill displayed in those losses.

Battling Nelson loses in 42 rounds against Joe Gans...Joe Gans loses in 15 to Sam Langford while fighting for the second consecutive day...Bob Fitzsimmons at 37 gives Jim Jeffries hell in their second fight...Billy Conn has Joe Louis on the ropes for 12 rounds before being KO'd...Lew Tendler makes Benny Leonard rise to ATGness to beat him in their second fight...Rocky Graziano is impossibly gallant in his loss to Tony Zale...Ezzard Charles, late in his career, becomes the only man to go 15 with Marciano...Tony DeMarco gets a standing ovation from Carmen Basilio's home crowd after being knocked out in Syracuse...Henry Cooper almost takes out Cassius Clay...Danny Lopez proves he has the goods despite losing to Bobby Chacon before they become champions...Ray Leonard becomes recognized as not just a pretty boy in losing to Duran...Ken Norton's rep improved after each of his two losses to Ali...Azumah Nelson burst onto the scene in a gallant loss to Chava...Rafael Marquez's rep was enhanced in his loss to Izzy in their third fight...Arturo Gatti's rep was enhanced in his loss to Mickey Ward...you get the point.

Now if you're asking a little different question like when has a loss led to a guy getting a big fight he might not otherwise have gotten because he performed well? Well, every time a high visibility rematch has been scheduled, right?