CHICAGO – The Bears dropped their preseason opener to the Kansas City Chiefs 24-20 Thursday night at Soldier Field, but they suffered an even bigger loss before the game.

First-round draft pick Chris Williams underwent surgery Wednesday night to repair a herniated disc in his lower back. The rookie left tackle has been sidelined since sustaining a back strain July 24 in the second training camp practice. When the muscle issue subsided, Williams was further evaluated on Tuesday after new symptoms associated with a disc problem first appeared.

Rookie running back Matt Forte rushed for 25 yards on seven carries in Thursday night's preseason loss to the Kansas City Chiefs.

Williams was initially treated with anti-inflammatory medicine and his muscle spasms abated. Based on his progress, he started working out on an adjacent field during practice, but as the anti-inflammatory medicine wore off, his condition plateaued and eventually worsened.

The condition is an entirely new issue that is unrelated to any previous back injury.

The Bears declined to give a timetable for Williams’ return, but indicated that they plan to keep the Vanderbilt product on the 53-man roster once the regular season begins.

On the field, Bears quarterbacks Kyle Orton and Rex Grossman were both solid but not spectacular with neither seemingly taking an edge in their competition for the starting position. Both managed the game well while operating an offense that didn’t commit a turnover.

Orton played the Bears’ first three series, completing 7 of 10 passes for 56 yards with no touchdowns or interceptions and an 83.8 passer rating. He looked sharp in connecting on passes of 11 yards to Rashied Davis along the sideline and 16 yards to Devin Hester and 12 yards to Desmond Clark over the middle.

Orton’s biggest miscue came when the ball squirted out of his hands while he was scrambling to his left looking for a receiver on third-and-10 from the Kansas City 15. After the quarterback recovered his own fumble for a 9-yard loss, Robbie Gould’s 42-yard field goal drew the Bears to within 7-3 with 6:51 remaining in the second quarter.

“I think we got some stuff to go back and look [at] on film and hopefully make some improvements and score some more points,” Orton said. “Personally, I thought I saw the field pretty well. I felt comfortable, and for the most part I thought I threw the ball very well. [There were] a couple batted balls, but other than that I thought I played pretty well.”

Replacing Orton with 4:31 remaining in the second quarter, Grossman completed 4 of 8 passes for 44 yards with 1 TD, no interceptions and a 106.2 passer rating before being replaced by rookie third-string quarterback Caleb Hanie midway through the third period.

Grossman’s best pass was a 19-yard completion to receiver Brandon Lloyd on a nice timing route along the sideline late in the first half.

But early in the second half, Grossman was sacked when he fell to the seat of his pants after getting his feet tangled with an offensive lineman. He then failed to connect with receiver Marty Booker on third down and was shown by television cameras shouting as he came off the field.

Despite injuries on the left side of the offensive line, Bears running backs excelled Thursday night. Like Orton, rookie running back Matt Forte played the Bears’ first three possessions, rushing for 25 yards on seven carries and catching a team-high three passes for 10 yards.

“The offensive line opened up some holes for me, and I got a little yardage,” Forte said. “It was good to get out here and get that first action of football. They were playing basic defense. It was all I thought it would be. Going up against our defense every day helped me out with adjusting to the speed of the game.”

Second-year pro Garrett Wolfe enhanced his chances of cementing a role this season with a 42-yard run and a 25-yard touchdown reception. On the run, Wolfe burst through the line of scrimmage and dashed down the left sideline before being dragged down at the Bears’ 48.

The 2007 third-round pick from Northern Illinois showed his explosiveness again midway through the third quarter when he took a short dump-off pass from Grossman in the middle of the field and dashed around right end and into the end zone, drawing the Bears to within 14-10.

Bears defensive tackle Anthony Adams sacks Chiefs backup quarterback Damon Huard in the second quarter of Thursday night's preseason opener.

Wolfe rushed for a game-high 64 yards on seven carries. His touchdown came one play after Bears linebacker Rod Wilson produced the game’s only takeaway by intercepting a Tyler Thigpen pass and returning it 12 yards to the Kansas City 25.

“We harp on turnovers and taking the ball away,” said coach Lovie Smith. “The one takeaway we did get led to a score, [but] we definitely need to get more of those.”

The Bears’ No. 1 defense settled down after a rough start. Opening the game with a 16-play, 81-yard drive that burned 8:45 off the clock, the Chiefs took a 7-0 lead on Larry Johnson’s 5-yard TD run up the middle on third-and-goal.

“I was not pleased with the opening drive,” Smith said. “Our defense can not allow that to happen. We had them in some third-and-long situations and we let them out. But that won’t happen to us a lot this year. We’ll learn from that; we’re better than that. I thought after that we settled down and did some good things.”

After the game’s opening drive, Chicago’s No. 1 defense permitted just 12 yards and no first downs on nine plays on Kansas City’s next three possessions.

With most starters no longer in the game on either side, the Chiefs took a 14-3 on Damon Huard’s 8-yard TD pass to receiver Maurice Price with :11 left in the first half. Price beat cornerback Trumaine McBride to cap an 8-play, 75-yard drive that took just 1:33.

Hanie’s 13-yard TD pass to receiver Brandon Rideau late in the third quarter capped a 12-play, 80-yard drive and gave the Bears a 17-14 lead. Rookie tight end Kellen Davis made a diving 25-yard catch of a Hanie pass along the right sideline on the previous play to set up the score.

Hanie displayed a strong arm and excellent athleticism, completing 9 of 16 passes for 101 yards with 1 TD, no interceptions and a 96.1 passer rating. The undrafted free agent from Colorado State also picked up a first down with an 18-yard scramble.

After the Chiefs tied the game 17-17 on Connor Barth’s 37-yard field goal early in the fourth quarter, Gould’s 37-yarder gave the Bears a 20-17 lead with 3:19 left in regulation.

Kansas City receiver Bobby Sippio, a former Chicago Rush star in the Arena Football League, then scored the game-winning TD on a 27-yard pass from Thigpen with 1:08 remaining.

Hanie threw for three first downs in the final minute, but rookie receivers Earl Bennett and Marcus Monk both dropped passes on the last drive. Hanie’s desperation heave from the Kansas City 45 fell incomplete on the game’s final play.