On July 29, the defending world champion Phillies acquired AL Cy Young Award winner Cliff Lee and outfielder Ben Francisco from the Cleveland Indians for pitchers Carlos Carrasco and Jason Knapp, infielder Jason Donald, and catcher Lou Marson.
If the Dodgers had traded Billingsley, that would have given them three lefty starters: Lee, Kershaw and Randy Wolf. Teams generally don't like to have more than two leftys in the rotation because most line-ups lean toward having more right-handed batters. And the Dodgers probably just couldn't stand to part with Kershaw. Who can blame them?