ONEILL'S VIEW Barcelona 0-0 Celtic

"It was a terrific performance," O'Neill told BBC Sport. "We were driven back all night.

"It was a fabulous effort - the players are all out on their feet. They were amazing to keep going like they did.

"Some of our younger players really came of age out there," added O'Neill after his side reached the last eight.

Nineteen-year-old goalkeeper David Marshall made a number of impressive stops in what was just his fifth start of the season.

"We just thought if we got a goal, we would have a chance but to keep a clean sheet in the Nou Camp was unbelievable," said Marshall.

"In the first half, they were saves I expected to make but I made a good one in the second period. I was just pleased to help the team.

"It was a long day in the hotel, especially when you know you are starting.

"But you have just got to deal with it as all the lads have done over the years."

Marshall was playing due to Robert Douglas' suspension and may have to make way for the more experienced keeper for Sunday's Old Firm derby against Rangers at Ibrox.

Teenager David Marshall was magnificent for Celtic

"I will just push him (Douglas) all the way and hopefully see what the manager thinks," added Marshall.

"I will just have to wait until Sunday and see what the manager does. If I'm picked, I'll have to do a job again."

O'Neill revealed Marshall had received a rapturous reception from his team-mates after the goalless draw.

The manager said: "He walked into the dressing room to fantastic applause from the rest of the side."

Celtic striker Henrik Larsson hailed Marshall's ice-cool display, but joked that his tender age had played its part.

"I think he is too young to have any nerves - he doesn't realise how big it was," said the Swede.

"He was tremendous - from the first minute of the game onwards.

"The save he made from Luis Garcia in the second half was outstanding.

"I don't think you can have a better full European debut so I'm very pleased for him."