Kansas City, Mo. ? Since being drafted in the fourth round in 2001, Monty Beisel has gone from defensive end to outside linebacker to middle linebacker then back to outside linebacker.

Mostly, he’s been a special-teams operative struggling to stand out.

Now, with injuries cutting a swath through the Kansas City linebacker corps, he’s probably going to start at middle linebacker Sept. 12 when the Chiefs and their revamped defense open the season at Denver.

For the former All-Big 12 Conference defensive end from Kansas State, it will be a completely new position: The reads are different and the responsibilities are changed.

But the expectations still will be high.

“First, we asked him to take a career gamble by moving to outside linebacker from defensive end,” Chiefs coach Dick Vermeil said. “When you ask a guy to lose all that weight and learn a new position, you’re asking him to take a chance.”

After working all training camp at outside linebacker, Beisel was switched inside when Kawika Mitchell sustained a high ankle sprain on Monday night against St. Louis.

Mitchell had gone into camp as the backup to Mike Maslowski, who set a team season record for tackles in 2002. But Maslowski has been slow to recover from knee surgery and could be out for the year.

Now that Mitchell’s out indefinitely, Beisel has a chance to capture a job — or fail miserably.

“It’s all about opportunity, especially in this league,” Beisel said. “There are a lot of guys around the NFL who get opportunities other guys don’t get. Unfortunately, mine has only been on special teams up to this point. Now I’m going to have to make the most of it and try to run with what I’ve been given.”

When he was switched to backup outside linebacker in 2002, he had to gain mobility. Working hard, he’s trimmed almost 40 pounds off his 6-foot-3 frame.

“It was over a span of about three years,” he said. “I feel a lot more comfortable.”

He was looking good at outside linebacker this summer, and some thought he might even push starter Scott Fujita.

Instead, Beisel will make his first start in the middle Saturday night when the Chiefs play host to the Cleveland Browns in their third exhibition game.

“Like I said, it’s tough, especially at this level when all of a sudden you’re playing a new position you never played before,” he said.

Maslowski, meanwhile, has yet to give Kansas City a decision on whether he will try to play on the still-sore knee or undergo season-ending surgery. All signs point toward his sitting out the year.

“I think within the week we’ll have everything defined as to what he’s going to do,” Vermeil said.

Maslowski hardly has practiced since the first week of training camp.

“He can’t practice on his knee right now, so it does not look good. He can’t play on it because of the pain,” Vermeil said. “I just told him I want him to do what he thinks is best for him.”

Maslowski’s absence the last two months of last season coincided with a collapse of the Chiefs defense, leading to the resignation of coordinator Greg Robinson and the hiring of Gunther Cunningham.

“He feels the pain and the problems with it,” Vermeil said. “I indirectly feel the pain because we need him and love him. But he’s not here. We go on.”

They’ll go on, at least through the season opener, with Beisel.

“It’s a whole different ball game inside,” Beisel said. “You get outside, you’re able to run a little bit more and freelance a little bit more. Inside, it’s just you and a couple of gaps and you have to guard your territory.

“I’m just going to try to do the best I can.”