Chip Kelly knows what his team is up against this Sunday when the New England Patriots make their Levi's® Stadium debut in Week 11.

"You're going against one of the best quarterbacks to ever play the game in Tom Brady," the San Francisco 49ers coach began, "a really good set of receivers, two outstanding tight ends. They can run the football. They're very balanced in terms of how they can attack you from an offensive standpoint and then Bill's (Belichick) defenses are always going to be well-coached and solid."

The 49ers (1-8) and Patriots (7-2) have experienced different seasons to say the least. San Francisco is coming off its eighth consecutive loss. New England, on the other hand, suffered its first defeat in five weeks since Brady returned from a four-game suspension.

"It's a huge task and a huge challenge for us this week," Kelly said.

The opponent certainly has everyone's focus inside of 49ers headquarters.

"Our guys were talking about it yesterday," Kelly said on Monday. "It obviously has their attention in terms of what we have to do. We've got to have a great week of preparation. You're probably talking about playing one of the best teams in football right now coming in this Sunday."

The Patriots rank eighth in yards per game (380.8) and sixth in points per game (26.8). Brady, a native of San Mateo, Calif., has thrown for 1,635 passing yards with 12 touchdowns and one interceptoin in five games this season.

"Obviously, he's a really good quarterback," defensive coordinator Jim O'Neil said on Tuesday. "They've got a lot of weapons around him. He's been in the same system for a really long time. So they have answers for everything. He gets them in the right plays. He's not a guy that you're going to trick or fool. He gets the ball out fast. There's not a lot of deficiencies in his game."

Kelly remains optimistic about his team's chances of pulling off an upset on Sunday. The 49ers are coming off a 23-20 road loss to the Arizona Cardinals. San Francisco held star running back David Johnson to 2.9 yards per carry on 19 rush attempts and held the Cardinals to three points in the second half. The points, however, came on a game-winning field goal as time expired.

 "I think you always have hope," Kelly said. "I don't think anybody just says, 'Let's take the week off because we can't win.'"

Recent reports suggest the Patriots could be without tight end Rob Gronkowski due to a punctured lung. With or without "Gronk," the 49ers must be prepared to defend Martellus Bennett, who leads the New England in receiving touchdowns (4) and is second on the team in catches (38) and receiving yards (504).

O'Neil shared some of the keys to defending large targets like Gronkowski and Bennett.

"You've got to do a good job playing to your leverage, and then you've just got to do a great job being violent at the reception point," the coordinator said. "If it is a high ball, you've got to get off the ground first, try to beat them to the spot. But it's a challenge. Their tight ends are huge."

Kelly-coached teams have had successful results agianst Belichick's clubs.

The Philadelphia Eagles beat the Patriots on the road last season, 35-28, in Week 13.

"It's an entirely different situation, but we've played them before, and I understand the challenge of it," Kelly said. "I think if you're a competitor you get excited about playing in games like this. You don't think of it as, 'Oh my God, we don't have any hope.' You get a chance to play against Tom Brady and Bill Belichick. If that doesn't get your blood boiling, then you're in the wrong sport."

San Francisco offensive coordinator Curtis Modkins pointed to New England's ability to utilize its ever-changing personnel as their biggest strength.

"They are always going to be well-coached," Modkins said. "They always play hard. You have to beat them offensively. They're not going to give you busted coverage or be out of gaps. You have to beat them. It's kind of how it's been as my experience with them. ... I think our guys are looking forward to the opportunity to prepare today, and we'll go from there."