Ramos' changes altered the Carling Cup final against Chelsea last month and the recent Premier League clash against the same opposition - and he looked to his bench again when Pompey looked set to earn a point at White Hart Lane.

With 20 minutes remaining Ramos took off a centre-back, introducing Bent for Michael Dawson, while O'Hara came on for Aaron Lennon.

Within 10 minutes, Bent nodded home after Dimitar Berbatov scuffed a shot into his path. Bent then raided down the right and crossed for O'Hara to tap into an unguarded net.

"We take off a defender when it is urgent," Ramos said. "It brings a risk and today it paid off, other times it doesn't pay off in the same way.

"The decisions to make changes are not made for the sake of it. It is to turn matches around. They have worked well. The players are aware of why we make them - a solution for a game that is blocked up."

Until the changes, the match looked to be fizzling out towards a goalless draw.

Dawson thumped a volley against the crossbar in the first half, David James made a couple of comfortable saves and Pascal Chimbonda went just wide from the edge of the area - but clear chances proved difficult to create.

Flowing football was made difficult by swirling wind, sleet and snow punctuating the match.

While Pompey were on the back foot for much of the time - not helped by a hamstring injury to Lassana Diarra on the eve of the match and Jermain Defoe being ineligible - they weathered the storm and almost scored just before Bent broke the deadlock.

Glen Johnson's cross caused goalkeeper Paul Robinson to hesitate and Kanu was presented with an open goal - but Didier Zokora raced back to clear.

Then came the two goals, in the 80th and 82nd minute.

"Benty opened up the whole match," said Spurs assistant boss Gus Poyet. "The substitutes don't always know how important they can be."

Pompey boss Harry Redknapp admitted his side have one eye on Wembley in a fortnight when they face West Brom in the FA Cup semi-final.

Redknapp also had Sol Campbell and Lauren out, while Sylvain Distin nearly missed the game as his wife was due to give birth.

"I was going to play (assistant) Tony Adams, he could still do it - he wouldn't let you down," Redknapp said.

The Pompey boss added: "Our priority is the cup, we have to try to beat West Brom and reach the final.

"It would have been nice to have taken a point but they have some good players. We are sixth and they are 11th and that shows you how well we have done."

Focus will inevitably now be on Bent and whether he can break the partnership of Robbie Keane and Berbatov.

"We know how many goals Robbie and Berba have scored - it's a good partnership," Poyet added. "But if he keeps coming on and scoring goals he will get his chance sooner or later."

Bent said: "It's good to come to do something and change the game. There is no point in me sulking about it and not doing anything when I come on.

"I have to keep going and see what happens. All I can do is keep plugging away and doing what I can do.

"They (Keane and Berbatov) have more than 40 goals between them so it is difficult, but I knew that before I got here. I'm ready for the challenge."