LAKE FOREST, Ill. – The Bears defense will be challenged both on the ground and in the air Sunday in Atlanta by the NFL’s leading rusher and a highly-touted promising young passer.

Running back Michael Turner and rookie quarterback Matt Ryan have led the surprising Falcons to a 3-2 start, putting Atlanta already just one victory shy of matching last season’s total.

Brian Urlacher and the Bears will look to remain in first place in the NFC North with a win Sunday against the Atlanta Falcons.

Turner is a bruising 5-10, 244-pounder who combines size, strength and speed. He has rushed for a league-high 543 yards and six touchdowns, an average of 109 yards per game.

In preparing to face Turner Sunday at the Georgia Dome, Bears linebackers coach Lloyd Lee apparently has described the running back to his players as “the modern day Jim Brown.”

“The guy’s physical,” said linebacker Lance Briggs. “He’s not going to go down with arm tackles. We have to play physical and rally around the ball. It’s a great challenge for us. It’s an opportunity for us to stop one of the best running backs in the game.”

“Guys hit him and he stays on his feet and is able to spin off and keep running,” said defensive lineman Israel Idonije. “We have to have that gang [tackling] mentality, which we have had. We do a good job of swarming and not letting one guy get in a situation where he has to make a tough tackle.”

Turner signed with the Falcons as a free agent in March after spending his first four NFL seasons as LaDainian Tomlinson’s backup with the San Diego Chargers. In his Atlanta debut, Turner rushed for 220 yards and 2 TDs on 20 carries in a 34-21 Week 1 win over the Detroit Lions.

“He’s definitely one of the best running backs in the league,” said defensive end Adewale Ogunleye. “He’s an explosive runner who breaks tackles. He’s the kind of guy I don’t want to see one-on-one with our DBs."

Turner reminds Ogunleye of his former Miami Dolphins teammate, Ricky Williams.

“[Williams] was really hard to bring down,” Ogunleye said. “His lower body was really strong and he’d run over the secondary a lot, and that’s what it looks like Turner is doing. You have to hit him squarely to get him down.”

The Bears defense and Falcons offense each rank eighth in the NFL, but that isn’t the only similarity between the teams. They're both coached by a man named Smith (Lovie and Mike), they have identical 3-2 records and they've lost to the same opponents, the Carolina Panthers and Tampa Bay Buccaneers.

In last Sunday’s win over the Lions, the Bears defense scored a touchdown on Charles Tillman’s 26-yard interception return, registered four sacks and allowed just 185 total yards.

In Turner and the speedy Jerious Norwood, Atlanta boasts an explosive thunder-and-lightning running back combination much like the ones the Bears have faced with Earnest Graham and Warrick Dunn against Tampa Bay and Jonathan Stewart and DeAngelo Williams versus Carolina.

“They have two different styles,” defensive coordinator Bob Babich said of Turner and Norwood. “They complement each other well. It’s a very good rushing offense. They have a good scheme along with two good running backs.”

Behind Turner and Norwood, the Falcons ground game ranks second in the NFL, averaging 180.6 yards per game.

Atlanta’s passing attack is fueled by Ryan, the third overall pick in the draft. The rookie quarterback has completed 71 of 131 passes for 863 yards with 4 TDs, 3 interceptions and a 75.3 passer rating that ranks 22nd in the NFL.

“He’s done some good things with their offense,” Briggs said. “He’s been able to be very effective. They do a lot of rolling out and creating some space for him to throw the ball. They have a good scheme and he works well in it.”

Operating a run-oriented offense, Ryan has yet to throw for more than 200 yards in a game. After being sacked four times in a Week 2 loss to Tampa Bay, he has only been sacked twice in Atlanta’s last three games.

“They’re doing a good job of getting him out on [bootlegs],” Ogunleye said. “They’re not leaving him back there by himself. He’s getting the ball out of his hands really quickly, which is good for their scheme.

"They have a great running attack which has been able to help them out. They’re a running team, so they’re not really leaving it up to him to make the big plays. All he has to do is go through and manage the game.”

Health beat: Starting cornerbacks Charles Tillman (shoulder) and Nate Vasher (wrist) both participated in practice without restrictions Thursday after being limited Wednesday. Linebacker Nick Roach (shoulder) was limited Thursday after not practicing Wednesday.

For the second straight day, defensive tackle Tommie Harris (knee) was limited and defensive tackle Anthony Adams (ankle) and wide receiver Brandon Lloyd (knee) did not practice.

For the Falcons, defensive tackle Jason Jefferson (ankle) and wide receivers Laurent Robinson (knee) and Roddy White (head) did not practice; and defensive tackle Grady Jackson (knee), center Todd McClure (calf), tight end Justin Peelle (knee), tackle Todd Weiner (knee) and guard Ben Wilkerson (chest) were limited.