Raiders Are Playing Catch-Up Football : NFL exhibition: Shell says offense, special teams must match performance of defense with regular season two weeks away.

With visions of quarterback Warren Moon and the Houston Oilers’ run-and-shoot offense dancing through their heads as the regular-season opener approaches, the Raiders will attempt to work out some kinks in today’s 1 p.m. exhibition game against the Chicago Bears at the Coliseum.

Last Monday night at Dallas, the Raiders’ first-team offense scored its first touchdown of the summer. The defense, a strength throughout, gave up yardage but allowed only four field goals in a 17-12 victory. The special teams? Well, fortunately, two practice games remain.

The bane of the 1990 season, their special teams continued to haunt the Raiders against the Cowboys, giving up kickoff returns of 54 and 45 yards.

Despite some lapses, Coach Art Shell says the Raiders are on a steady course toward Houston for the Sept. 1 opener.

“The object for this team is to improve in every aspect of the game,” he said. “We have to improve on special teams; we have to continue to improve in our offensive scheme. Defensively, we have to continue to do the things we’ve been doing. We’re getting pretty good there. Offensively, we need to catch up.”

Early problems on offense might be traced to instability along the line, not an area you want lagging when your coach is a Hall of Fame left tackle. Strides were made this week, beginning Tuesday when Pro Bowl center Don Mosebar ended his monthlong holdout and reported.

Wednesday, the team made another switch, replacing Rory Graves at left tackle with Bruce Wilkerson. Graves, much maligned during a holding-plagued 1989 season, was a solid starter last year. But a return to bad habits has landed him on the bench for now.

Wilkerson was the team’s starter at right tackle until last summer, when he strained left knee ligaments and was out for eight weeks. When he returned, replacement Steve Wright was playing so well that Shell didn’t want to upset the line’s chemistry.

Wilkerson accepted his role as a capable backup.

“I lost my job to injury,” he said this week. “Coming back, I never really felt 100%. I could play, but I wasn’t 100%. The team was winning, so I played my role. The bottom line is to win football games, with or without me. As long as we’re winning football games, I don’t have any quarrels with anything.”

Wilkerson hasn’t played much at left tackle in his five-year career, although he did alternate there with John Clay as a rookie.

“Basically, it’s the same position (as right tackle),” he said. “The assignments are the same. It’s just opposite. But I’ve been on the left side ever since I got back from the injury.”

Wilkerson hopes to join in the Raider fun this year after watching the team run to the AFC West title in 1990.

“The regret of you not being in the lineup kind of haunts the back of your mind,” he said.

Other Raider positions, of course, remain unresolved. Although Steve Beuerlein followed Jay Schroeder against Dallas, and Vince Evans did not play at all, Shell maintained this week that Evans was still the team’s No. 2 quarterback.

Shell said Evans was given the night off to make way for the debut of rookie Todd Marinovich, the team’s first-round draft pick. Shell said Evans would play today against Chicago.

Today is also an important day for Raiders on the bubble. The team must reduce its roster from 80 to 60 Tuesday.

“This is a very competitive football team,” Shell said. “It’s important that some of them play well. As I’ve said before, they’re being watched and graded in practice, also. So the game is not always the standard. It’s helpful.”