I will show you the scans.
Here is the scan of Naruto blocking Madara's attack -
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Here is the scan of Sasuke attacking Madara, but Madara not fighting back. Instead he stops Sasuke movement to ask him a question -
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I posted the scan again for you to view because he need to view them again. Naruto arms are in front of his body. A clear indication that he blocked the attack. There was not exclamation mark or question mark showing Naruto was surprise because he wasn't. He was knock down by the force of the attack. I'm not surprise since Madara was showed to gather chakra before his attack and that was a living Madara with the senju power body that Kabuto further enhanced.
Madara never attacked Sasuke so Sasuke didn't have to worry about being attacked. He only wanted to talk. It took Sasuke attacking him 3 times before he decided to attack Sasuke. He let himself be injured so he could stop Sasuke without hurting him. He has the 1st power healing ability so that injury was not a concern.