Although Tottenham are now within touching distance of a second Wembley appearance in two years, their first-half performance displayed exactly why Harry Redknapp would like to make so many changes to his squad this month.

Jermain Defoe was reintroduced to the Tottenham fans before the game after completing his £16million return to White Hart Lane from Portsmouth yesterday and the arrival of the England striker will not be the end of Redknapp's January spending.

The Spurs boss complained after the game that his squad were "badly balanced" and that they lacked strength in depth. On the evidence of the first- half, it is impossible to argue with his reasoning, and Stewart Downing, Stephen Appiah and Steve Finnan remain transfer targets.

For 45 minutes of the first leg of this semi-final, Carling Cup holders Spurs were outclassed by Burnley, making a nonsense of the frequent claim that there is a huge gap between the Premier League and the Championship.

Predictably, the home side got a flea in their ear from Redknapp at half-time, and their response was spot-on, with all four goals coming in the first 22 minutes of the second period. But their fightback cannot mask the alarming problems exposed in the first-half.

Where Burnley were fluent, Spurs were ragged. Where Owen Coyle's team were patient and inventive in their build-up, their hosts' only attacking ploy was to feed Aaron Lennon on the right. And when the little winger has an off night - as he did against Burnley - he is lucky if a single cross finds a team-mate. Chairman Daniel Levy spent about £70m last summer and they are ready to part with serious money again this month. But Redknapp will reflect that the man who turned this game in their favour is a player who cost the club nothing.

As soon as Jamie O'Hara, who came through the Spurs youth system after joining from Arsenal in 2003 as a 17-year-old, replaced the ill David Bentley after the break, the tide turned.

His right-wing corner was headed in by Michael Dawson two minutes after the break for the equaliser, before O'Hara put Spurs ahead five minutes later when his left-footed volley squirmed under Brian Jensen.

O'Hara's most important contribution, though, was in defence. In the first half, Burnley right-winger Chris Eagles had tormented Gareth Bale. To make matters worse, Bale received little assistance from Bentley and was often left one-on-one against Eagles.

Indeed, Eagles' movement in the first- half made him almost impossible to mark and it was no surprise to see him create the first goal. The former Manchester United winger tricked his way past Bale before setting up Martin Paterson for a tap-in after 15 minutes.

After the break, though, Eagles was nothing like as influential and that was thanks mainly to O'Hara's diligence. His work was so good, in fact, that Burnley boss Coyle decided to switch Eagles to the left wing.

This was perhaps O'Hara's most significant performance since making his Spurs debut in December last year and he admitted: "It was great to come on and make such an impact.

"The first 20 minutes of the second- half were a bit of a blur. It was a great feeling to come on, score a goal, and be involved in two of the other goals. Hopefully we can reproduce our second-half display in the second leg at Burnley."

O'Hara's corner that set up Dawson's goal was their first decent delivery of the evening from the wings and he quickly followed it up by putting Spurs 2-1 in front with his close-range volley.Roman Pavlyuchenko maintained his record of scoring in every round of the competition when he drilled in a fine third goal in the 65th minute and shortly afterwards O'Hara's excellent free-kick forced Michael Duff to head past his own goalkeeper.

Despite his misgivings about his squad, Redknapp is confident his team have done enough to be able to reach the final on 1 March, where they would face either Derby or United.

Redknapp said: "The tie is not over but if you cannot defend a three-goal lead, with good Premier League players, then there is something wrong.

"But we are naive. I look at us at times and some of the young players do things when a bit of know-how is missing. Burnley had us on the rack and I could not see that end result coming.

"At the break, I told them, 'I am going to find out an awful lot in the second- half about a lot of you', because we needed to show what we were made of as we were under a lot of pressure.

"It was the first time I have really laid into the players at half-time but it did the trick. We responded fantastically. Jamie O'Hara was excellent."

All Spurs fans' eyes now turn to Sunday's Premier League fixture at Wigan, when Defoe is expected to make his second "debut" for a club who are above the relegation zone on goal difference alone. And if Redknapp has his way, the 26-year-old may not be the only new face in his starting XI at the JJB Stadium.