ALEX McLeish looks weary. He's been manager of Rangers for four years now and the strain is clear in his increasingly saggy features. Each draw or defeat - and sometimes even a win - is met by calls to quit from a spoiled generation of Rangers supporters, who know no middle ground between ugly triumphalism and self-indulgent caterwauling. McLeish's media interviews are prickly affairs, with any hint of criticism taken as a personal jibe. Setbacks are explained away with a surly lack of good grace; Hibs' tactical superiority in a 3-0 win at Ibrox in August was dismissed as sheer luck.

I met Alex McLeish once, in 1988. Then, he was in his prime as a player, an imposing centre-half for Aberdeen and Scotland whose defensive partnership with Willie Miller overawed many a striker by reputation alone. Off the field, he was a softer character. I met him once at the Oldmeldrum Sports, an old-style gala in the north-east of Scotland where home-bakes and raffles were as important as any display of athletic excellence. I was a 13-year-old Aberdeen fan, dumbstruck as I stood in line before one of my heros, waiting for a signed photo. McLeish, the star attraction at the gala, was warm and chatty, unperturbed by the long queue snaking back from the foldaway table he was stuck behind. His off-field self-assurance matched the ease with which he strolled through most matches.

The contrast with the McLeish of 2005 is stark. Today, he's a truculent, embattled figure, whose jitteriness is betrayed by eccentric after-match analyses. Last Wednesday he blamed the boos that followed the Champions League draw with Artmedia Bratislava on the Slovakians' exuberant celebrations at the final whistle.

He's not the first Old Firm manager to undergo such a transformation. Martin O'Neill used to be one of the more engaging BBC pundits, his straight-talking analysis laced with a sense of mischief. Years into the Celtic job, however, and he became a moodier figure who found offence too easily. When Aberdeen players celebrated a 2-0 win in December 2001, following a series of thumpings by Celtic, he churlishly barked that they'd acted like they'd won the league. His successor, Gordon Strachan, already seems possessed of a deeply furrowed brow and rattiness far removed from his once impish demeanour.

To manage an Old Firm team is to put up with the expectation that every match should be won. But for many fans it's not just a case of wanting to wind up the local rivals; this sporting rivalry is fuelled by swaggering sectarianism. Celtic was formed in the 19th century as a project to help poor Irish immigrant Catholics in Glasgow. Protestants then started to gravitate towards Rangers. The legacy is a simmering menace whenever the two teams meet, which frequently boils over on the city's steets. Some young men have died for wearing the wrong colour of shirt.

The media blames football thuggery on an aberrant minority of social outcasts. That explanation doesn't hold at Ibrox and Parkhead, where sectarian banners and songs celebrating terrorist attrocities are common currency. When sporting rivalry curdles into such a deeply unpleasant conflict, it's no wonder Alex McLeish looks so sour.