Although Tottenham are firm favourites to reach their second successive Carling Cup Final, tonight's opponents Burnley have already knocked out three London clubs - and could make a strong case for Spurs being their weakest opponents yet from the capital.

Fulham, Chelsea and Arsenal have all been despatched by Owen Coyle's impressive Championship side on their remarkable run to the last four. All three clubs are above holders Tottenham in the Premier League table and Burnley will feel confident about their chances over two legs.

The Lancashire club beat Chelsea at Stamford Bridge on penalties after a 1-1 draw in the fourth round in November. They had already overcome Fulham 1-0 at Turf Moor in round three and went on to defeat Arsenal 2-0 in the quarter-finals last month.

Indeed, such is Burnley's strength at home - they have lost only two of their 13 games there in the Championship this season - that Spurs will need a convincing victory at White Hart Lane tonight if their minds are to be at rest when they travel north for the second leg in two weeks' time.

Spurs boss Harry Redknapp knows all about the difficulties of facing Championship opponents. His Portsmouth side beat five clubs from the second tier - including Cardiff in the final - on their way to lifting the FA Cup last season, winning all of those matches by only one goal.

Redknapp said: "I saw Burnley on Saturday [in their 0-0 draw at Queens Park Rangers in the FA Cup]. They have done well this season. They are well organised, with some experienced players, and have been on a fantastic run.

"Owen Coyle has done a great job and they can't be underestimated.

"With Portsmouth last season, we were drawn away against Ipswich and Preston in the FA Cup and both games were a struggle. Every one of the five Championship sides gave us a fantastic game and we were lucky to win some of them. But we are so close to the final and it is a fantastic chance for us to try to retain the trophy. Staying in the Premier League is the priority but the Carling Cup is very important to us.

"Winning it for its own sake is more important than getting into Europe again, as it was when we won the FA Cup with Portsmouth."

With his side enjoying a return to form in the 3-1 FA Cup win over Wigan last Friday, Redknapp will be pleased to learn that Burnley have little desire to look for a 0-0 draw at White Hart Lane.

Spurs have struggled this season when confronted with opponents who play defensively but Burnley manager Coyle insisted: "We will not go to White Hart Lane and be negative. We have some really talented players who can create and cause problems in wide areas and Spurs will know they have been in a game.

"We hope still to be in the tie by the final whistle, and to have a chance of causing an upset at Turf Moor. If Spurs play well over two legs, we know they are probably the favourites to go through.

"But we have caused a few upsets this season, and we have players capable of causing another one, so let's hope we can do it."

Coyle's quiet confidence is in contrast to Redknapp's concern about the size and quality of his own squad.

The transfer window has been open for just six days but Redknapp is already on the brink of clinching a deal to bring back Jermain Defoe to White Hart Lane, and has made offers for Middlesbrough winger Stewart Downing and West Ham striker Craig Bellamy.

Redknapp wants a full-back, at least one striker and a left-footed player to balance his midfield, while he is also looking at potential loan deals.

The Ghana midfielder Stephen Appiah could also earn a deal until the end of the season if he impresses in training this week. Less than two months ago, Redknapp's priority would have been a new goalkeeper, but Heurelho Gomes' improvement since Tony Parks' arrival as goalkeeping coach has been remarkable. Redknapp added: "It is pretty obvious that we need to spend in this transfer window.

"We have a very small squad but it is hard to find the right players to come in. Gomes has been a real plus for us, though.

"To come through the kind of pressure he was under to show the form he is producing clearly proves what he is made of.

"Tony Parks has done a great job with him. He has been in great form and has made some outstanding saves in recent matches."

Redknapp and Spurs hope the Brazilian will not be forced into more stunning stops tonight.