All-Ireland SFC Qualifier Derry v Dublin: Ian O'Riordan asks Tyrone boss Mickey Harte what Dublin can expect at the weekend.

One question has dominated the minds of Dublin football supporters this week: Just exactly how good is this Derry team?

All that is certain is that they've changed a lot of faces since denying Dublin a place in the All-Ireland final in 1993, in what was their last championship meeting, and that Saturday's qualifier is being played in some place called Clones.

But little is known about Derry's current form, their strengths and weaknesses, and the players most likely to influence the result.

For Tyrone football manager Mickey Harte, all those matters were addressed in great detail in the build-up to last month's Ulster championship quarter-final, and so he's as certain as anyone now as to what sort of challenge they will present.

"First of all I think people do underestimate this Derry team. Part of it is because there were playing in Division Two of the league, the fact that they didn't clinch promotion, and lost their last game to Longford. So people started thinking Derry wouldn't be there this year.

"But Derry are never far away. I mean they are virtually playing with the same team that came so close to Galway there two years ago, the year Galway went on to win the All-Ireland.

"And while the likes of Anthony Tohill might be in the twilight of his career, he's still a hugely influential figure. So I think Derry are right up there with the best teams in the country. People just seem to miss that point for some reason."

Harte has seen his team cross-examined twice by Derry this year, firstly in the drawn quarter-final, and again in the replay, where Tyrone comfortably progressed by nine points. On the basis of those two performances he is clear on where Derry can and will cause problems.

"Paddy Bradley is a prolific scorer. He had a terrific game against us the first day, and was obviously watched a lot more the second day. But if he's coming in fresh to a team like Dublin that don't know him well he will certainly cause problems.

"And I think Paul McFlynn is one of the best players that Derry have. He plays at wing back, but can play at centre back or wing back.

"He's always very effective and can control the game for Derry. Then you have to talk about their stoppers at the back, the likes of Seán Martin Lockhart and Niall McCusker. So they have a great balance right across the field."

And there were, admits Harte, external problems which contributed to Derry's poor performance in the replay: "There was the death that week of a young child in Ballinderry. Her brother was playing for the Derry minors, and that game was cancelled, and it certainly didn't help the Derry performance.

"But if Derry do hold one ace card, then it is their full-back line, and those two defenders of Lockhart and McCusker. They give very little away, and are good man-to-man markers. Without doubt they're very capable of negating free-flowing scoring."

Having also witnessed Dublin at close hand at Parnell Park in the league, a game where Dublin sneaked a one-point win over the eventual champions, Harte is not about to underestimate Dublin.

"I certainly think Dublin have a great midfield in Ciarán Whelan and Darren Magee. They had a bad game against Laois, but I still think Dublin could easily have won that game had a few more things gone right for them on the day.

"So it was definitely unfair to write the likes of Whelan off on the result of one game. There will always be days when things don't go right, and when we played them in the league he was hugely influential, and I was wondering how anyone could deal with him when he's on song. But every player is entitled to an off day, and I think it just gives them an appetite to come back better the next day."

While Clones might sound like a foreign land to Dublin supporters, the pitch factor, says Harte, will have no bearing on the result.

"Derry might take a little more comfort about where they are playing, but when you have class players like Dublin do it shouldn't matter where they play.

"And, strangely enough, people talk about Clones being a tight pitch. It's virtually as big as Croke Park. So they'll have just as much room to play football as they would have in Croke Park. And the fact is pitches don't win matches. Possession wins matches."