The quarterback, who spent last season with the St Louis Rams before being cut this summer, rejoined the team yesterday as cover for the injured starter.
The 24-year-old told the team's website: "It's been a tough six weeks, and it feels like two years. Just kind of sitting around waiting and just trying to get back in here.
"It's unfortunate, Sam's a good friend and he was really playing well this year, so it's not an ideal situation, but I've got a job to do.
"Offensively, I think the biggest benefit of coming back here is knowing the system. The terminology is all familiar and you hit the ground running. In a way, it feels like you never left."