American Football: Cowboy back in town: Matt Tench on the balance of power for today's meeting of the superpowers in American football's NFC title match

FOR six years Charles Haley played for the San Francisco 49ers, quickly establishing himself as one of the team's outstanding defensive talents, and was three times elected to the Pro Bowl. He was an integral part of two Super Bowl-winning sides. In August he joined the Dallas Cowboys. Haley returns to Candlestick Park for the first time for today's NFC Championship game between the 49ers and Cowboys. It will not be a meeting of old friends.

Even during his time in the Bay area, Haley was not a popular figure. His intimidating, often devastating play was matched by a volatile off-the-field personality that alienated team-mates and coaching staff in equal measure. The most publicised incident came after a loss to the Los Angeles Raiders in 1991. Haley got so upset with the offense that Ronnie Lott, once a 49er but by then playing for the Raiders, had to be summoned from the opposition locker-room to calm him down.

Matters were made worse when the 49ers signed Tim Green from Green Bay. The similarities between Haley and Green were unavoidable: both played outside linebacker, both did so very well, and both upset a lot of people. They never got on and the feud between the two was said to include a fist fight and petty pranks.

By the beginning of this season George Seifert, the 49er head coach, had had enough. Haley was traded to Dallas for the relatively knock-down price of a second-round pick in this year's draft, and a third-rounder next year. Haley has been almost silent about his return for most of the week, but there can be no doubt he brings a 17-stone grudge to today's game.

The Cowboys, as might be expected, profess delight in Haley. He has recorded only four sacks - Green has 17 - but has been a key figure in the dramatic improvement of their defense, which has seen them rise in the rankings from 17th to first. 'He's really done a good job for us,' Jimmy Johnson, the Dallas head coach, said. 'I heard all the stories prior to making the trade and it did give us some concern. But the thing I did hear was that he was a very hard worker on the field and he was a tremendous competitor. He has come in and really fit in well with our players.'

Haley himself insists he did not have a problem in San Francisco until Bill Walsh left as head coach in 1989. It was then that he acquired his reputation. 'So finally, I'm projected as a lunatic, a crazy, raging animal and I'm traded,' he told the New York Times. 'I guess it will never change as long as we live in a society where negativism is a plus.'

Haley's performance is likely to be one of the key factors in a mouth-watering match-up. The winner will play the victor of the AFC Championship game in Miami, where Buffalo are the visitors. Such is the present disparity between NFC and AFC that few doubt that whoever wins in San Francisco will go on to claim the Super Bowl.

Both Dallas and San Francisco boast gifted, versatile offenses capable of racking up plenty of points. To stop them, the opposing defenses need to disrupt early and prevent a rhythm becoming established. This is where Haley comes in. His incursions could provide the big play which will settle a game almost too close to call.

Forced to pick a winner, it is hard to back against San Francisco who, for all Dallas's youthful brilliance, have a territorial advantage and the edge in experience. Still there may be a Charles Haley factor. Steve Wallace, whose job it will largely be to stop him, said: 'If he's human for this game, then we're going to have a decent shot at stopping him.' Then, perhaps wary of sounding over-confident, Wallace added: 'But, you never know. The guy may show up and play unreal.'