Celtic head coach John Barnes sends his players into the fray against Rangers today knowing he might have to reassess their talents in the light of another Old Firm examination. Barnes thought he knew his players until he saw them exposed by Rangers in a 4-2 Ibrox defeat in November.

But he had to think again after that reverse which came just days after Celtic's dismal UEFA Cup exit to Lyon and was a harsh wakeup call to Barnes and his Celtic side of the realities of attaining success.

The same individuals who had out-played the likes of Aberdeen were suddenly found wanting, with Barnes sharing the blame for an inflexible 4-2-2-2 formation which was stifling Celtic's potential.

Rangers will see a very different Celtic side today at Parkhead - but Barnes still fears he will not know how different his team are until the game is under way.

He said: "The trouble is I thought we looked okay until the Rangers and Lyon matches, which was a higher quality of opposition than we'd faced before then. You really don't know where you are until you play those teams.

"I think we can score goals against Rangers, but they can score goals against us too. They've quality players who can hurt teams, and you cannot man-mark all of them.

"But I believe we have players who can do similar things. I also think we're better now than the last time we faced them. I don't know if we'd been lulled into a false sense of security before that.

"The point is when they beat us it gave us a kick up the behind. We now know we have to do the right things for the full 90 minutes.

"Even when we were doing well at earlier parts of the season I was ranting and raving at the players when they were 5-0 up because I knew we'd be punished on other days against different teams, and so it proved."

Celtic's position going into today's Old Firm clash is certainly precarious, because defeat would offer Rangers the opportunity to move seven points ahead in the table with a game in hand.

When asked if a defeat would spell the end for Celtic's season, Barnes retorted: "We would have to expect to come back. But we have to look at it as saying if we win we're only a point behind.

"But again if we win it doesn't mean we'll win the title. It's still, however, an opportunity for us to get points off them.

"If you look at the points dropped by Celtic and Rangers so far I don't think that is necessarily going to be the situation. I can always see teams taking points off both of the Old Firm.

"Unfortunately as it stands this season they have taken more points off us than they have Rangers - but away from the championship when Celtic play Rangers the fans want to be top dog.

"I don't see it being as straightforward as they will win the league if they beat us. Likewise vice-versa, but if we beat them it will be a bit of revenge and will keep the fans happy."

Barnes's only doubt today is Danish midfielder Morten Wieghorst, although he does have the option of bringing club captain Tom Boyd and Norwegian utility player Vidar Riseth back after injury. Barnes is keen to play down the significance of the last Old Firm game when Celtic were a minute away from going into half-time ahead.

But he accepts with a revised 3-52 formation Celtic have more to offer, and there is no prospect of Lubomir Moravcik again being put on the bench, as he was at Ibrox. Barnes said: "With derby matches, particularly the intensity of this one, I don't think previous games count for much. I don't think much can be taken from one game into another - they're totally one-offs."