Kroos criticised the Catalans' two most recent performances against PSG and Real on his 'Einfach mal Luppen' podcast, which he hosts with his brother Felix.
In last weekend's Clasico, Barca suffered their first LaLiga defeat, losing 1-2. Kroos said Real Madrid ensured "that Barcelona's top players in particular did not feel comfortable, did not get into their rhythm and then made mistakes they would not normally make".
Kroos explained: "When Barcelona cannot get at their opponents for a while, they are not good at defending. If Barcelona cannot get at them with their pressing, they have major problems with switches of play or balls in behind. The game against Paris showed that too. They then have major problems because they still defend in a very high-risk way."
Alongside his criticism, Kroos praised the tactical approach of Barcelona's respective opponents. His former club Real and their coach Jose Mourinho particularly impressed him. "I think, and this is clear praise for Mourinho, that Real set themselves up superbly against Barcelona, especially without the ball."
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Real Madrid produced a "superbly bold" performance against a Barca side who had been unbeaten in the league until then. They could have got more out of the game, too. "With the ball, Real had many more opportunities to hurt them even more," Kroos said, with the Catalans at times struggling considerably without possession.
In recent meetings, Barcelona had mostly had the upper hand. Kroos saw a different approach from Real this time: "Of course, they had spells when all they did was defend. After the equaliser, everyone would have taken a 1-1 draw. But I think they played a really bold game without the ball for 60, 65 minutes, saying: 'Okay, we're not going to sit back here; we're going to close them down high up the pitch.' Whenever Barcelona played backwards, they pushed up boldly. That was not the case in the last Clasicos. They spent the whole game chasing after them and conceded one goal after another," Kroos said.
The narrow win moved Real to within three points of the Catalans in the table. Barcelona remain top with 27 points from ten matches, while city rivals Atletico Madrid are second, level on points with Real.