Tom Brady has said that the New England Patriots face their toughest game of the season when they play the San Francisco 49ers on Sunday.
The two teams are both ranked second in their conferences, and are the bookmakers' favourites to make the Super Bowl.
Brady told SportsRadioInterviews.com: "[The 49ers'] defense is one of the best that I've ever seen so this is going to be a totally different challenge. We're going to have to be at our best this week.
"Certainly this week is going to be our biggest challenge we've had all year."
The Patriots' quarterback began preparing for the fixture after their game against the New York Jets three weeks ago.
