GLASGOW, April 2, 2008 (AFP) - Rangers manager Walter Smith admits his side could be a victim of their own success ahead of the visit of Portuguese side Sporting Lisbon in the first leg of their UEFA Cup quarter final on Thursday.

The Ibrox side are on course to complete a domestic treble and are also hoping to add the European trophy to their season's haul.

Having already won the Scottish League Cup, Rangers are in the quarter finals of the Scottish Cup and have a six point lead at the top of the Scottish Premier League with a game in hand.

In comparison, Lisbon currently lie fifth in the Portuguese League and lost on penalties in the League Cup final.

Although Sporting still have the Portuguese Cup and UEFA Cup to play for, Smith is worried Rangers' efforts on four fronts could hand their European opponents an advantage.

'Sporting have had a little bit of an indifferent season by their high standards,' commented Smith.

'They lost a number of top players last summer and have found it difficult to gel together to find the consistency they had last season.

'But they still have individual players who can cause any teams problems and have the capability to be an extremely good side in any given game.

'Because their championship is beyond them now all their focus will be on the UEFA Cup and that makes them extremely dangerous.

'When you are still involved in four competitions the games come thick and fast and it's difficult to go from one aspect to another.

'Having said that, we're delighted to be in the UEFA Cup at this stage and we look forward to all our games.'

In Rangers' European games this season - including in the Champions League - and many of their domestic matches, Smith has preferred to operate with only one striker and five in midfield.

Smith disagrees with any criticism - some from Rangers supporters - that his side are overly defensive.

However, the Rangers boss admits he hopes they can cause more chances against Sporting than they managed against Werder Bremen - who they beat 2-1 on aggregate in the last round.

'In the last round we could not have asked for a more difficult tie than against Werder Bremen and we had to work extremely hard in both legs,' admitted Smith.

'This time we hope to cause Sporting more problems than we caused Bremen.

'I think the defensive aspect of our play is a little bit exaggerated. We have a way of playing that has been successful in knockout competitions and we won't alter that too much.

'But we know it might be necessary to change the formation and tactics to try and cause problems for Sporting.'

Rangers have been boosted by the news midfielders Kevin Thomson and French-Algerian Brahim Hemdani have both recovered from shin and groin injuries respectively.

Although Sporting Lisbon have been struggling domestically, on Sunday they secured a confidence boosting 4-1 league win over Naval with Brazilian sharpshooter Liedson notching up a double.

Manager Paulo Bento believes his side can take that confidence into Thursday's match in Glasgow and grab a vital away goal to take into the second leg the following Thursday.

'The result against Naval has restored a lot of our confidence,' he said.

'This season we have scored away from home in the Champions League and the UEFA Cup and I believe we'll continue that on Thursday.'