As far as I can tell, if the Giants and Tigers face off in the World Series, this will be the year where the World Series participants have had the most direct involvement with regards to homefield advantage since the All-Star format changed.
Verlander started for the AL this year and got lit up, taking the loss. Cain started for the NL and got the win. And Melky (though tainted) won the MVP as a Giant. The three players who had arguably the most influence on the outcome of the game would come from the two World Series teams.