COLLISION COURSE FOR ERRATIC TEAMS : CHARGERS, STEELERS TOUGH TO FIGURE.

Byline: Alan Robinson Associated Press 

They are two of the NFL's most erratic and unpredictable forces - Mike Tomczak's right arm and the San Diego Chargers' can't-get-it-right offense.

One week, they are a model of smooth efficiency. The next, they are error-prone and incapable of any forward progress, thereby ruining any momentum they may have spent a month building.

Now, beginning with a must-win game today for the Chargers (7-6) and a better-not-lose game for Tomczak's Steelers (9-4), neither knows what to expect during a December fraught with potential pitfalls for both teams.

Will Tomczak again be the steadying influence who dodged his career-long history of inconsistency to jump-start the Steelers to a 5-1 record? Or will he again be the underconfident passer whose mechanics were so flawed in last week's 31-17 loss in Baltimore he struggled to throw even a screen pass?

For San Diego, former USC quarterback Sean Salisbury starts for the injured Stan Humphries, who sustained a concussion in last week's 45-7 loss at home to New England. But it's anybody's guess which offense he will run.

Will it be the one that self-destructed with six turnovers against New England and never got it going in a 25-17 loss to Tampa Bay? Or the one that outslugged Kansas City on the road two weeks ago?

``We need leadership to step up,'' Chargers cornerback Darrien Gordon said. ``We don't need leaders telling people what to do or making pep talks. We need leaders who are going to perform on the field, especially in a must-win game like this.''

He could have made the same speech in the Steelers' locker room.

Here it is early December, and the defending AFC champions still don't know where they are or where they're going. The same team that is 0-4 in AFC Central road games - potentially, the worst ever for a division champion - also won Monday night games at Buffalo and Kansas City.

The Steelers can secure their fourth division title in five seasons with one more victory or one more loss by Houston (7-6).

``Maybe what we need to realize is we're a damn good football team . . . and we just have to start believing it,'' Tomczak said.

Tomczak didn't make many believers in Baltimore, despite statistics that on first glance (18 of 36, 221 yards, two touchdowns) seemed worthy of a passing grade. He constantly underthrew or overthrew his receivers, benefiting only when Andre Hastings or Charles Johnson made excellent catches.

The loss to the Ravens (3-9) was especially troubling to the Steelers, who have talked repeatedly of securing the No. 2 seed behind Denver (12-1) for the AFC playoffs. Currently, the Patriots, Steelers, Bills and Chiefs are tied at 9-4, but Kansas City only can be a wild-card team.

``We've still got three football games left against pretty good teams: San Diego, San Francisco and Carolina,'' Steelers linebacker Chad Brown said. ``At this point, we've almost lost control of that (home field), so we've got to take care of what's in front of us.''

His remarks echo those of coach Bill Cowher, who is preaching this message: Don't panic. We're still 9-4 and in good shape. Everything we want is ahead of us.

``We're the Steelers, we're at home for our next two games and I like that very much,'' Cowher said.

But, for the first time, the Steelers seem distressed by the season-long run of injuries that has depleted their defense. Pro Bowl defensive back Carnell Lake (sprained knee ligament) will likely miss the rest of the season, and Brown, who has a team-high 11 sacks, is playing on a bum ankle. Tight end Mark Bruener, whose blocking has helped Jerome Bettis to 10 100-yard games, is out until next season after needing knee surgery.

The Chargers' medical chart isn't much better, not with Humphries out for at least one game. Salisbury isn't a disaster as a reliever, but has been troubled by turnovers, throwing seven interceptions and only five TD passes.

One positive: Tony Martin, who has 70 catches, while matching Lance Alworth's team record with 14 touchdown catches.