MARATHON man Carlos Cuellar will rack up his 50th appearance of the season in tomorrow's Old Firm crunch at Ibrox.

And the big Spaniard - who is on course to play more games in one season than any player in the club's history - admits he's desperate to mark his half-century with three crucial SPL points.

Player of the Year candidate Cuellar has missed just one match this season, the 6-0 Scottish Cup romp against East Stirling back in January when he was an unused sub.

The £2.4million purchase from Osasuna has unquestionably been Walter Smith's best signing in his second spell at the club.

And he now looks set to overtake the Gers appearance record for one campaign that has stood for almost 30 years.

That record is held jointly by Peter McCloy and Bobby Russell, who played in all 61 Rangers matches in season 1978/79.

With a minimum of 13 games left, starting tomorrow against Gordon Strachan's men, the rock solid Spanish defender should set a new mark this term.

Cuellar's poor displays can be counted on one hand - he was ropey in Gers' 4-2 defeat at Tynecastle in September and also could have done better when Lyon won 3-0 at Ibrox in the Champions League - and his consistency has been amazing.

Undoubtedly, Smith's side's chances of winning a fourth consecutive Glasgow derby will be helped if the 27-year-old stays in the form he has displayed for most of the season.

Fatigue certainly doesn't appear to be a factor for Cuellar, who said: "I have obviously never played as many games as this in my career.

"But I am enjoying it. It's not a problem for me to play two games a week and it's great to be involved in so many big matches in so many different competitions.

"I wasn't aware that I could set a record this season, and I'll just keep taking it match by match.

"My attitude is always to do the best I can in every match for the team, and for our fans, and I'll just carry that on until the end of the season."

Cuellar's only Old Firm experience was the 3-0 win over their great rivals back in October.

He admits that people never stopped telling him what the Glasgow derby would be like in the lead-up to the match.

But he was blown away by the atmosphere, and admits that these are the kind of games every player should relish playing in.

"It was a good day for us and we deserved to win the match," said Cuellar. "It was a fantastic experience and made better because we won.

"I had seen an Old Firm game on TV, as we watched a DVD of Rangers playing Celtic before Osasuna played Rangers in the Uefa Cup last season.

"But to play in the game was something else. The passion from the stands was unbelievable and the game was intense."

He went on: "It's just one of those matches that you want to win so much, as you know what it means in terms of the season and for the fans."

Celtic, stung by that poor display and with a need to avoid defeat tomorrow at Ibrox, are likely to be a different prospect this time for Cuellar and his team-mates.

But, with the confidence of an unbeaten SPL run that stretches back five months and 17 games, the defender is hopeful that Rangers can take another step towards the championship.

"It would be a big win for us, but also for Celtic, and I am sure that both teams will be doing everything they can to get the points," he admitted.

"We have a small lead at the moment in the championship, but we are not assuming anything because there are so many games left and we need to stay focused.

"Derby games can be un- predictable. But, of course, we know what is at stake and how important winning could be."

Again, as so often in these games, mistakes or moments of individual magic could prove to be crucial.

Cuellar hopes Rangers can have that match-winner in their ranks, but points to the team ethic that has carried them to this position as their strongest asset.

"We have players who can produce special moments in games, from goalkeeper Allan McGregor right through," Cuellar added.

"For instance, our captain, Barry Ferguson, is just so important to us. He is the focal point of the team and the inspiration.

"But the spirit we have here has really impressed me this season, and I believe that is the biggest asset in our side."