Thursday morning in Edinburgh and Gary Mackay is rushing out the door on the way to a Dundee match against Rangers in the under-18 league. As he goes, his mobile phone rings for the tenth time in half an hour.

It's a call confirming a meeting he has arranged in Dumfries with Queen of the South manager John Connolly for Friday morning. Seconds later, it rings again with one of the stable of players he runs through his Kickstart 2000 football agency asking for some advice.

Indeed, the only time the man who played for Hearts for 17 years will get the chance to turn off his phone and forget his busy lifestyle will be tomorrow, when he attends the Edinburgh derby at Easter Road.

Hard to imagine a Hearts legend relaxing at the home of their oldest enemy but the fact that Mackay, who will be there to give some expert radio analysis, has never hidden his allegiances for the maroon has meant he should be given some peace from the Hibernian sup-porters in the main stand.

At 39 years old, Mackay has become one of the most respected football agents in the game, with a pool of top managers and players on his books. He is discreet about precisely whom he represents, although it is well known that his stable includes Stevie Fulton of Kilmarnock, Garry O'Connor of Hibs, and Derek Fleming of Partick Thistle.

It is as a player that he made his name, though, and, as he sits in the radio gantry at Easter Road tomorrow, Mackay, whose 737 games for the Tynecastle club in all competitions is a club record, can draw on an incredible record of personal success in the Edinburgh derby.

''I remember a statistician telling me I'd played in 51 Edinburgh derby games over 17 years and only suffered five defeats in all that time,'' said the former Hearts midfielder whose father, Peter, is a life-long Hibs supporter. ''It's a record I'm proud of and maybe back then we had a bit more belief than Hibs.''

Mackay grins when asked if he will have mixed emotions about the game tomorrow on the grounds that one of his clients is O'Connor, whose career has blossomed of late. That improvement is put down by many inside the game to sound advice from Mackay and Bobby Williamson, the Hibs manager.

''In a perfect world Garry will score a hat trick tomorrow but Hearts will win 4-3,'' said Mackay. ''And, if it happens, I'll regret not putting a bet on it.''

Talking to Mackay, you understand the emotion that the Edinburgh derby brings out in players and, for the former Hearts midfielder, it's something that never goes away.

''The Old Firm derby meant nothing to me,'' said Mackay. ''The Glasgow derby does have an atmosphere all of its own but, for me and many others, the Hearts against Hibs game is still the main one.

''I was talking to Kenny Black [the former Rangers and Hearts player] the other day and we agreed we'd pay money to start our careers all over again and have the chance once again to play in big matches like the Edinburgh derby.

''I have great enthusiasm for what I do now but your time in football passes you by so quickly. I realise that, as an agent, you give your players financial and off-the-field behavioural guidance but I believe the best advice you can give anyone in the game is to make the most of it as you never know when it might all come to an end.''

Mackay's career came to an end in March 1997 by which time he earned four Scotland caps and played in two Scottish Cup finals and one League Cup final. He was on the losing side each day. He also played on the infamous day, from a Hearts point of view, when they lost to Dundee in the final game of the season which allowed Celtic to win the league.

However, it is the encounters against Hibs which stay freshest in his memories and he has strong powers of recall of most of the games. ''As a Hearts supporter, I always put more pressure on myself to try and beat Hibs,''said Mackay. ''I used to get myself into a terrible state the night before games early in my career, such was my excitement about playing Hibs. I couldn't sleep at times.

''I firmly believe that having local knowledge of the Edinburgh derby is important and that's why I think Grant Brebner will be a big player for Hibs tomorrow. He's a Hibs supporter, knows the passion of the occasion, played for most of the 5-1 defeat at Tynecastle earlier in the season, and will be putting pressure on himself to do well.''

That was just what Mackay used to do when he starred in numerous Hearts teams which turned over Hibs time and time again. He may be just a spectator tomorrow but the man who is still idolised by the Tynecastle faithful will still want the team he graced for 17 years to do him proud.