ITS possibilities in the public consciousness poised somewhere between an agrarian out rage and the best match of the season, tomorrow's Bank of Ireland Ulster football semi final in Clones reignites a bitter, but seminal rivalry between Tyrone and Derry.

Over the five years since the current players first locked horns in the championship, a lot has changed on the Ulster landscape. The balance of power within the province has become nationally relevant and the implications of what was once a neighbourhood squabble are now huge.

Within the respective teams, reputations have been made and unmade in the course of this fixture and even tomorrow, outstanding issues remain - and not just from last year's controversial semi final when Tyrone, short two players, astonishingly overcame a three point deficit and the wind in a tumultuous second half.

It will be the third championship meeting in just over five years, during which time both sides have developed into top rank championship contenders - something that would have seemed as distant as Mars when they played each other at Omagh on May 19th, 1991.

That preliminary round marked the beginning of an evolution that would ultimately take Tyrone to an All Ireland final (at last) and Derry to the prize itself. For Derry, most of the 1993 All Ireland winning team were in place and they were embarking on a four year period during which they either won the title or lost to the eventual winners.

Tyrone's situation was less well formed. A few of the side that lost last September's All Ireland final to Dublin were already on the team but it was in transition.

John Donnelly was the manager for a three year period between Art McRory's two spells in charge. "I took over in 1989," he says. "The team had won the Ulster championship but were just coming out of Division Three and as a unit were past it. So I had to bring in new players. That day (1991), we had a number of young players. We had the edge on them but Derry got the break.

In the last 20 years Derry have had a lot of the breaks, winning championship meetings by a precise ratio of two to one. As in 91, there were matches that Tyrone should have won but the converse also applied. In truth, Derry exercise no particular voodoo over their neighbours and historically, the championship tally splits roughly 50-50.

Last Tuesday after a low key training session in Clones, Tyrone staged a press night. Neither the town nor the Creighton Hotel looked to best advantage in the dreary, wet and overcast weather but the players and management seemed relaxed. Joint manager Eugene McKenna sketched the alternative scenarios, in answer to a question about the extent of the benefit to the team's morale of last year's achievements.

According to McKenna, many Tyrone players felt their careers were on the line against Derry last year add there was almost a desperation to win. This year, the mood is more one of self assurance. Whether the gain in confidence is qualified by a diminished hunger will be one of the day's main findings.

Have Tyrone reversed Derry's recent dominance and are they about to prove it by beating them for a second successive championship for the first time in 40 years? On a crucially related topic, is Peter Canavan's recent ascent to the status of the best full forward in the country permanent and is the under 21 class of 1991-92 ready to translate the achievement to senior level?

For one player in particular, Adrian Cush, the world is spinning around again. Once spoken of in the same breath as Canavan and rated as highly, the former under 21 star has endured years of injury and declining confidence to the extent that his contribution last year was largely made from the substitutes' bench.

Hopes and expectations that he is regaining his true form go on the line with the rest of Tyrone's ambitions but he is part of a new half forward line, designed to enhance the team's scoring potential and encourage opposing defenders to worry about more than one sixth of the Ulster champions' attack.

Although their paths have diverged sharply in the meantime, Cush and Canavan shared All Ireland under 21 success in the seismic 20 point dusting of Kerry in 1991. They were the first of the crop to graduate to senior (in fact, Canavan played at the top level before playing under 21).

While Cush waits to prove his rehabilitation tomorrow, it is easy to forget that Canavan himself suffered a difficult and prolonged period of settling in. "It was," says John Donnelly, "to be expected. When I was in charge, most of them were under 21s. In my first year, Peter had already played senior; by my last year, he was still under 21 and also playing colleges (Sigerson Cup).

"They train over the winter and there's no sophistication, it's a real sledging match with a hard man image. Then he's trying to concentrate on under 21 and championship.

"I said to Art McRory a couple of years ago: Peter is going to deliver. He's too good a player not to deliver now that he's got only senior (inter county) and his club to concentrate on."

In 1991, against Derry, both Cush and Canavan played a week after beating Kerry in the under 21 final. Cush scored the goal in a 1-8/1-9 defeat but Canavan, struggling with an injured back, was unable to make an impression and had to be substituted in the second half.

The following year was the defining one for relations between the counties. Both developed through impressive League campaigns and contested that year's final. With that year's Ulster preliminary round match due a fortnight later, stakes were high at Croke Park.

"I always maintained," says Donnelly, "whoever won the League would win the championship match. Two weeks wasn't enough time to regain the psychological edge." The assessment proved gloomily accurate. Tyrone outplayed their opponents but a calamity in defence and some impressive, late finishing saw Derry home.

IN Celtic Park, 14 days later, there were no excuses. On a tighter pitch, a thoroughly confident Derry crushed Tyrone not so much on the scoreboard but deep down.

The two matches were a cumulative disaster for Cush. His reputation was high going into that League final but the failure to make much of an impact - he did scramble a goal at Celtic Park - has followed him since. Some in the county say his confidence has never recovered.

This profound demolition job was the work of Gary Coleman, who tomorrow in his recently adopted position of full back, marks Canavan. There had been no early indications that Cush would be in trouble; quite the contrary.

"People say that Celtic Park was the root of the problem," says Danny Ball, coach of the successful under 21 sides, "but at under 21 level, he tormented Derry. He ran Gary Coleman ragged the first year we won, ran him ragged. Derry had no one to mark him."

Donnelly offers this perspective: "Apart from the physical end, one thing Peter Canavan has is mental toughness. Physical toughness is important but the real crunch a thing is mental toughness, to be able to say right, no matter how things roll, I'm going to make a contribution. Canavan has it Cush doesn't have the same toughness."

At the same time, there has been dedication and courage in the face of severe set backs. "You've to remember as well, he's had terrible problems with a back injury," says Donnelly. "Doctors told him not to play anymore but he went ahead."

"He had a back injury for a long time says Ball. "No management has had a really good run with him." He also feels that Cush wasn't helped by circumstances that fateful fortnight, four years ago.

The way the team had been going, Paul Donnelly and Cush used to combine very well on the right wing. Donnelly was a ball winner and Cush had the football, but the partnership was broken up.

When Art McRory and Eugene McKenna took up the reins of team management, they encountered the same team building problems as Donnelly - a lack of physically big players to solidify the team. The problem endures. "We've trawled the county for big players," said McRory during the week, "but if they're not there there'd nothing we can do."

Nonetheless, the upturn in fortunes over the last two years has been steady. With many of the under 21s coming through and Canavan developing into the game's most influential player, McRory and McKenna have led the county to one Ulster final and last year, an All Ireland final.

Cush had a hard year during last summer's championship run. Taken off in the first match against Fermanagh, he made a couple of highly effective appearances as substitute and looked to be finding the panache and scoring touch that had characterised his best days to date.

Again, problems. Injury ruled him out of any active participation in the All Ireland final - a match that Tyrone lost by only a point despite some good second half possession and chances. Cush could be forgiven if tantalising thoughts about his potential impact on that situation occur now and then.

Another season started three weeks ago, with Cush in the starting line up. His perseverance is impressive. Working in England for the Tyrone based engineering company Powerscreen which sponsors the Players' All Stars, Cush has commuted week in, week out.

"Well, he's put in a lot of hard work over there," says McRory. Scoring regularly, he's a big asset, a class act. He's home every week, so we moved training to Saturday. He works for Powerscreen and is moving into sales with them. Adrian's very popular and totally dedicated."

Cush's former managers are equally positive. "Even in 1992, people forget that he destroyed Dublin twice that League. He hasn't done himself justice, says Donnelly.

"I rate him very, very highly," says Ball, "and I don't think Tyrone people have seen the best of him yet.