We can say that Croatia was very lucky in last two games, but they did not play nor close to how they can play. Which is the reason for such poor performances we can only speculate, but England will be a real test for them. It is possible that the match Croatia-England be very different from what Croatia show in last 2 games, they need to start play much better to reach the finals.
No doubt they have great players from Real Madrid, Barcelona, Juventus, Liverpool and some others big football clubs, but England is a much better team then Denmark or Russia. I am sure it will be one more interesting match, maybe again with extra time and a lottery of penalties kicks.
I think it's the other way around and Croatia will be a real test for England. England played very poorly against Columbia and were lucky to scrap through. If Rodriguez was playing I think they would have lost. People are giving too much credit to England I think and they've had a very easy drive to where they are now and even in the semis they have the easiest route to the final. The real test for them will be either France or Belgium as to how great they truly are but they've got to get past Croatia first who I doubt will be a pushover.
I don't know what's up with Croatia but after that flashy thrashing of Argentina they are playing with great difficulties vs mediocre teams and now they have played 240 minutes plus penalties in the knockout stage.
Mediocre teams just play more defensively since they have less "resources" to actually go for the win, they just have a defensive gameplan and nothing more, like Russia for example (or Sweden, England had a rought time trying to get past their defence yesterday), it's just really difficult to create chances and thrash your opponent when they're in full defensive mode. Big teams have an offensive mentality, meaning that they're more likely to leave open spaces, and we saw how Croatia managed to exploit that weakness vs Argentina (though Argentina was simply a trainwreck in every single match in this WC).
I think there is some truth in what you both say, this will be a completely different match for Croatia since England probably will not play like Russia or Denmark. This will mean more space for attackers and a possible match with more goals, but on the other side it is semi-final game and maybe both teams have different tactics for this game.
English media completely underestimate Croatia and they are confident in the final, but this is just a bigger incentive for the opposing team. In reality both teams have almost equal chances to win in this game.
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