Who Is The Draw?

Box Office Mojo had this to say in its write-up of Guardians of the Galaxy's successful opening weekend, "Characters that initially seemed like liabilities—Rocket Raccoon and Groot, specifically—wound up being a major draw, particularly with A-list actors Bradley Cooper and Vin Diesel providing vocal support." My question is, did Bradley Cooper or Vin Diesel really contribute to the characters being major draws? Vin Diesel did almost nothing. And Bradley Cooper had only one or two lines that ever made it into any trailers or commercials. Seems to me that it was almost 100% Chris Pratt in the commercials.