By Steve Ginsburg
Buffalo, off to their worst start in 25 years, squandered a 14-point lead but came back with a gritty effort before losing 37-34 on a 38-yard field goal four minutes into overtime.
"We showed we can compete with one of the better teams in the league, scratch and claw and fight back," said quarterback Ryan Fitzpatrick, who had four touchdowns in the loss.
"But every single one of those guys in that locker room is disappointed that we didn't come out on top."
The Bills lost their sixth straight game despite racking up 506 yards, the most the Ravens have allowed since 2000.
Buffalo stunned the crowd of 72,000 at M&T Bank Stadium as Fitzpatrick helped steer the league's 30th-ranked offense to a 14-point lead in the second quarter.
The Bills then self-destructed and allowed 10 points during the final minute before halftime to take a slim 24-20 lead into the locker room.
The Ravens scored a touchdown sixteen seconds into the third quarter to take a 27-24 lead and added another during the final minute of the quarter for a 10-point cushion.
But the resilient Bills fought back to force overtime on a 50-yard field goal by Rian Lindell with four seconds to play.
"I'm really proud of the way we fought back. There's no quit in this football team. It's frustrating, especially to lose that way," said Fitzpatrick.
"We're going to get over the hump."
Cundiff's game-winning kick was set up when Baltimore's Ray Lewis stripped tight end Shawn Nelson of the ball at the Bills 45. An unnecessary roughness penalty to Buffalo after the play moved the ball to the Bills 29 and sealed their fate.
Still in search of their first win, Buffalo travels to Kansas City next week to take on the 4-2 Chiefs.
"In this locker room, we don't feel like an 0-6 team," said running back Fred Jackson. "We feel like we are better than that. The reality is we're 0-6 but we're going to keep plugging at it.
(Editing by Frank Pingue)