AceShowbiz - Ben Affleck had no idea who "Gossip Girl" star Blake Lively was when she auditioned for his latest movie - and he was so stunned by her talent he hired her on the spot. The actor/director was unaware of Lively's fame when she tried out for a role in "The Town", and was convinced she would be no good in front of the cameras.

But he was so impressed with the 22 year old's performance he handed her the role immediately - and re-wrote the part of single-mum Krista to make it more suitable for a younger actress. Affleck tells Esquire magazine, "The whole movie kind of hinges in a lot of ways on her performance, and I knew it was going to be the hardest part to cast."

"This girl came in, and no one had said to me beforehand, 'Hey, look for this person.' And obviously she was really attractive, and so I thought, 'Oh, here comes some blonde girl.' She came in, did one reading, and just crushed it. I was sort of stunned. I said, 'Jeez, you know, that was really f**king good. Who are you?' She didn't mention that she was on a television show. I just said, 'Look, there's no alternative. I don't have a second choice (in casting this role).'"

And Affleck is convinced Lively has a big future in Hollywood. He adds, "I want to be on the record because I think she's really going to blow up, and I want to look like the smart guy. I didn't quite discover her, but at least I want to say I bought the stock when it wasn't $500 a share."