The studio had a third-person action adventure Call of Duty, and was on it for "about six months." It never left prototype as Modern Warfare 3 'called them'.
"The opportunity to work on the biggest thing in the industry with Infinity Ward, that's demonstrated that they know how to do exceptional software, was just an opportunity" they couldn't miss, said Michael Condrey, co-founder of Sledgehammer Games.
"There's a lot of people on the team who have worked on Call of Duty before, who have worked on first-person shooters before, so there's a lot of built-in knowledge about the first-person shooter genre and a lot of passionate gamers."
"Some guys on the floor are tenth level prestige in Black Ops."
The action adventure project lasted half a year and never went past a prototype, however there's a high chance it will be revisited by the studio.
"We came on board to make a third person action adventure game, in the Call of Duty franchise, and we were working on it about six months," continued Condrey. "We had a prototype together that was pretty compelling, and it looked really good."
Activision's Eric Hirshberg wants Sledgehammer's Call of Duty: "They were originally working on an extension of the Call of Duty franchise into an action/adventure genre and that's a game I still want to play," explained the publishing boss.
"That's a supreme, incredible group doing that. All I can say is right now they're 100% focused on Modern Warfare 3." Sledgehammer Games was formed by former EA studio bosses Glen Schofield and Michael Condrey in 2009.
Call of Duty: Modern Warfare 3 releases on Xbox 360, PS3 and PC November 8th.