To speak in a metaphor - nine separate women can't make a baby in a month. What makes you think ten can?
Straight-up adding people to a video game project doesn't always equal more getting done, particularly with a code-base as huge as Madden's most likely is. The credits scroll is already hundreds of people long and development of the game spans two teams, one in Florida and one in Texas.
There are plenty of resources on the game.