Barcelona must address their defensive frailties after being 'outplayed' by 'brilliant' Bayern Munich, Graeme Souness told Sky Sports.
The La Liga leaders suffered their heaviest aggregate defeat in their history as Bayern stormed into the Champions League final with a 3-0 win at the Nou Camp, following last week's 4-0 triumph at the Allianz Arena.
While Jupp Heynckes men celebrated reaching the Wembley showpiece, where they will meet Borussia Dortmund in the first ever all-German Champions League final, Souness said Barcelona must focus on strengthening their backline after being exposed by Arjen Robben and Thomas Muller, either side of a Gerard Pique own goal, on Wednesday night.
However, the former Liverpool midfielder also had plenty of praise for Bayern Munich, who he says never looked like being trouble by Barcelona in the second leg encounter.
"Bayern arrived in a great situation but I'm stunned," said Souness. "I'm sitting in the Nou Camp and the scoreboard is showing Barcelona have lost 0-7 over two legs.
"This season we've been talking about Barcelona being the best club side ever but they've been completely out-played, out-thought, out-muscled and out-gunned over two games by an excellent team.
"For me, Bayern don't have a weakness; they're rock solid at the back and up front they've got some players with real imagination.
"However, unlike last night (Tuesday), where Real Madrid had Dortmund rocking in the first 15-20 minutes and at the end of the game, Barcelona never got a finger on Bayern. What saves did Manuel Neuer have to make?
"As for their defence, Barcelona have been dominating football without having to build a solid backline - and now they need to address the centre of defence. They need to get two defenders who can defend first and foremost.
"Their choice [when signing defenders] seems to be [their ability to play] football from the back and defending secondary. But there's a lesson to be learnt from the way Bayern and Dortmund play."
Meanwhile, Jamie Redknapp believes this defeat could signal the decline of a Barcelona side which has dominated European football in recent seasons - and indicate the dawning of an era of German domination.
"Are Barcelona in decline? Yes, I think they are," said the Sky Sports pundit.
"Sergio Busquets, Andres Iniesta and Xavi is as good a midfield there is in world football but defensively this has been coming. There is talk of Victor Valdes leaving in the summer, they can't get away with patching Carles Puyol up, while David Villa looks a shadow of himself.
"Yes, there was no Lionel Messi and he transcends this team and takes them to a different dimension - but there is a fragility to their squad. There's no depth. Bayern were bringing on internationals while Barcelona were bringing on kids.
"I feel they need to bring in some players in the summer to freshen it up, but it does go in trends. We had a great French team with Patrick Vieira, Zinedine Zidane and I thought 'this is it, they are going to dominate football forever'. But then you have a few players retire and now French football is in decline.
"Spain are having their time and it looks like Germany are going to have their time as well."
However, despite Bayern's superb semi-final display, former Munich midfielder Michael Ballack says they are not certainties to sink Dortmund in the final - despite leading them by 20 points at the top of the Bundesliga.
The ex-Germany captain said Bayern's performances against Barcelona had surprised football experts and fans in his homeland, but reigning league champions Dortmund still have the capability to cause an upset in the final.
"At the moment Bayern are the best side in Europe," said Ballack.
"This was a demonstration - beating Barcelona 4-0 and 3-0 over two legs is amazing. Nobody in Germany expected this. We knew they were in really good shape and have had a fantastic season but to beat Barcelona in this way is outstanding.
"However, if I know [Dortmund boss] Jurgen Klopp he will tell the Borussia Dortmund players they can beat them - and they can do it, especially in one game.
"They have had a few fantastic games in the Champions League this year, such as against Real, and Bayern are not really happy playing Dortmund.
"To be beaten by a German team, by Dortmund would hurt Bayern a lot - especially after second places in the league over the last three years.
"There's a chance for Dortmund and they have a team who can beat Bayern in one game. Klopp is a great motivator and I'm sure he'll motivate them a lot."