Despite the loss of some key personnel, the Baltimore Ravens expect to build off a successful 2008 season. The Kansas City Chiefs, meanwhile, hope a new look throughout the organization will help them bounce back from a disappointing effort a year ago.

A pair of teams with something to prove face each other to open the season Sunday in Baltimore.

Baltimore won nine of its final 11 contests to finish 11-5, earn an AFC wild card berth then reach the conference championship game before losing 23-14 to eventual Super Bowl champion Pittsburgh last season. Kansas City, meanwhile, had the AFC's worst mark at 2-14, leading to a serious overhaul within the organization.

The Chiefs, who haven't won a playoff game since the 1993 season and lost all but six of their last 33 contests, fired head coach Herman Edwards and replaced him with former Arizona offensive coordinator Todd Haley.

Scott Pioli, the longtime vice president of player personnel with New England, is the new general manager and Matt Cassel -- who shined as Tom Brady's replacement a year ago with the Patriots -- was given a six-year, $63 million deal to guide the offense.

"I don't know when we're going to win, but we're going to win," Pioli said. "Until the time we win, it's going to be nothing but hard work."

Most of the work might need to be done on defense where Kansas City allowed 27.5 points per game and set an embarrassing NFL record by recording 10 sacks last season.

Veteran linebacker Mike Vrabel was brought over from New England and first-round pick Tyson Jackson from LSU has looked strong at defensive end in the new 3-4 alignment. Despite going 0-4 in the preseason, the Chiefs had seven sacks.

"I'm encouraged defensively overall," Haley said. "A lot of guys were asked to do some different things, some things they weren't used to doing. And most of them responded."

Haley's immediate concern, however, is Cassel, who injured his left knee in a preseason game Aug. 29.

Cassel -- who went 10-5 and threw for 3,693 yards with 21 touchdowns during his breakout 2008 season -- is taking part in individual drills in practice, but his status is uncertain.

"I don't know that we're going to have an answer right up until we play," said Haley, who will also serve as offensive coordinator after firing Chan Gailey during the preseason.

Former first-round pick Brodie Croyle would likely start if Cassel can't, a move that would seem to put the Chiefs at a huge disadvantage against Baltimore's stingy defense that was second in the NFL in total yards allowed last season with 261.1 per game.

"I had to play the Ravens a bunch, and there isn't one time you ever look forward to it," Haley said.

With 10-time Pro Bowl tight end Tony Gonzalez now in Atlanta and Cassel's status up in the air, the Chiefs could lean on veteran running back Larry Johnson, who appears poised to rebound after injuries and legal troubles helped limit him to 1,433 yards and eight TDs in 20 games over the last two seasons.

Johnson rushed for 120 yards against Baltimore on Dec. 10, 2006, the last time the Ravens allowed a 100-yard rusher -- a streak that's covered 35 games.

While the Ravens have loftier goals this season, former defensive coordinator Rex Ryan is now the head coach of the New York Jets and brought former linebacker Bart Scott with him.

Linebackers Ray Lewis and Terrell Suggs still anchor a unit that ranked first in total defense while going 4-0 in the preseason. Veteran safety Ed Reed returns after leading the NFL with nine interceptions in 2008.

While the Ravens appear confident again on defense, they'll hope the offense can continue to show improvement under second-year quarterback Joe Flacco.

With Flacco starting every game and throwing for 2,971 yards with 14 TDs, Baltimore averaged 24.1 points per contest and may have took some opposing defenses by surprise last season.

"We've got to get better because we know there is no defense that is going to overlook us," offensive coordinator Cam Cameron said. "Maybe we got overlooked a little bit last year."

While the receiving corps remains somewhat a concern, the Ravens feature a talented backfield of Ray Rice (454 rushing yards in 2008), Willis McGahee (671 yards, seven TDs) and Le'Ron McClain (902 yards, 10 TDs).

"If you're going to defeat us, you're going to defeat us as a team," Lewis said. "When we step on the field, we're one heartbeat, bottom line."

Kansas City, which looks to avoid a fourth straight season-opening loss, is 3-1 all-time against the Ravens and 3-0 in Baltimore.

Despite opening 2008 with a 17-10 win over Cincinnati, Baltimore has dropped five of its last seven openers.