Aaron Williams, playing cornerback, records two interceptions as Buffalo defeats Baltimore to improve to 2-2 on the season.

Coming into Sunday's game against the Ravens, the Bills had four changes to their starting lineup. In true Buffalo Bill fashion, in other words bad luck, all four of the changes were in the secondary.

The Bills were only facing the defending Super Bowl champions, fresh off an impressive victory over a Houston team expected to contend for an AFC title. Joe Flacco had his success against the revamped group, but it wasn't enough.

Buffalo defeated Baltimore 23-20 on Sunday at Ralph Wilson Stadium thanks to a strong effort from their secondary. Aaron Williams, Jim Leonhard, Da'Norris Searcy and Justin Rogers helped slow down a Raven air attack to secure the Bills second win of the year.

"I felt like I played good and I can't complain about two interceptions, but the defense helped me out out there," said Williams, who finished with two interceptions and four tackles. "You never know in this league, you have to keep going. When we have momentum going our way, the sky is the limit."

Williams won the starting safety spot after training camp, but an injury to Leodis McKelvin put him at left cornerback on Sunday opposite Rogers. Former Raven Leonhard, who didn't even sign with the Buffalo until Sept. 2, started at strong safety and Searcy played free.

With a slowed Ray Rice, Baltimore became one dimensional and the Bills were able to take advantage. Flacco finished 25-of-50 for 347 yards and two touchdowns, but he also threw five interceptions with three going to the secondary.

"I thought the defense played extremely well, especially on third down and what they did," said Doug Marrone, Buffalo head coach. "I thought they created turnovers. Obviously the guys in the back end were doing a great job of covering."

Williams hobbled around the locker room after the game but the pain wasn't bothering him during interviews. After you've played the best game of your professional career you tend to ignore pain.

Williams set the tone with a first quarter interception where he stepped in front of Tandon Doss to set up Buffalo's first score of the game. He showed his athleticism on his second interception, picking off Flacco as he tried to connect with Torrey Smith in the end zone.

Williams caught Smith from behind on a 74-yard pass in the third quarter. The Ravens, despite being in the red zone, had to settle for a field goal later in the possession.

"I think on the back end we were being more physical with the receivers," Williams said. "We really emphasized putting hands on receivers. Last week we didn't do a good job of putting hands on receivers. During this week we wanted to be more physical."

With his team up 13-7 early in the second quarter, Leonhard made an integral interception in Baltimore territory. The turnover set up Fred Jackson's 16-yard touchdown run to put the Bills up 20-7.

Leonhard nearly had a forced fumble and recovery in the second quarter, but the play was overturned. he former Wisconsin standout finished with four tackles.

"I think Jimmy is doing an outstanding job and we would be in a very, very tough diction if Jimmy wasn't able to come in there and do it," Marrone said. "He communicates very well, he really helps us on the back end and has been able to make plays for us. We're extremely happy with his performance."

Sunday's effort from the defense was probably what fans were hoping for when defensive coordinator Mike Pettine was brought over from the Jets this offseason. The Ravens rushed for only 24 yards and Flacco was sacked four times.

"I think that is a sign of respect, when you get a team who runs the ball as well as they do to only run it twice in the second half," Leonhard said. "You have to give credit to the guys up front. You just have to hold on and make plays, and we did."