It wouldn't. Ladson never said it would though, he just said he expected he would play well under Rizzo. He left open whether he would play well under other GMs as well. If I had to guess, though, I'd say that Ladson imagines that he would put more effort towards full recovery for Rizzo because he feels indebted to him. Personally I doubt motivational issues are what's kept Webb out of the majors for the last two years, but since Ladson appears to believe that effort, intangibles and attitude are all just as important as physical ability I can easily see this being his thought process.