The quarterback has been without his top five receivers from the 2012 season so far this year.
The 36-year-old told reporters: "We've faced some different challenges. I think in the NFL, a lot of teams face challenges it's just really how you deal with them. We've lost some guys, dealt with some issues, like every other team.
"We're handling them OK, we're 5-1. It's a decent start. It doesn't really get you anywhere at this point and I think we're still looking to make improvements.
"I think that's the most important thing, to try to improve every day in practice and the walkthroughs and hopefully it ultimately translates to better execution over the course of the season. But we're not really where we need to be right now; we're trying to get there."
The Patriots face the New York Jets this weekend.