Former Newcastle captain Alan Shearer was talking to BBC Radio 5 Live Breakfast about Tuesday's Champions League game between the Magpies and Barcelona (20:00 GMT).
"It doesn't get much bigger. One of the biggest clubs in the world with some of the biggest players and best players in the world," he said.
"It'll be a huge test for Newcastle. They'll have to be right on it on every single position.
"Newcastle have worked extremely hard and done extremely well in the Champions League this season – a lot better than they have in the league – they've earned the right to play one of the biggest and it should be a great occasion."
Manchester City beat Newcastle 3-1 in the FA Cup on Saturday.
"Obviously knocked out of the FA Cup at the weekend, which was disappointing… particularly the second-half performance which was weak," said Shearer.
"You've always got a right of reply as a player and a manager. What better way to reply than hopefully beating Barcelona. It's going to be tough.
"I think there will be lots of goals because of the way that both teams have defended, particularly Newcastle have been really poor defensively this season and Barcelona play this high line.
"I've watched them, worked on Barcelona a couple of times this season, particularly when they played at Stamford Bridge, when they scored three goals and could've been a lot more.
"If Newcastle get their system right tonight and I'm pretty sure they'll play a lot of pace up front because that reason then I think they will cause them problems.
"But it's at the other end that we have to try and keep them out. With the attacking talent that Barcelona have, that's easier said than done.
"I think it'll be a high-scoring game. That means hopefully goals. I'm going to be a romantic and go for another 3-2 win for Newcastle."
