I fail to see even some slight compensation for the pawn after 5...Nxd4 6.b4 Bb6.
This has some point if you substitute 4...d6 with 4...Nf6, because now Black has to take with the bishop (or pawn, which is a Max Lange proper). But still, his compensation is not clear at all.
In a blitz game, I had played 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. 0-0 d6 and I had premoved 5. d4--
I did lose the game but was wondering if d4 was such a radical notion after all. As a gambit, I believe it gained me good tempo and initiative, and was wondering if their was any real analysis and if there was even a refutation. If 5. ... Nxd4, 6. b4 is strong which can go in these sequences: (b4) Bxb4 7. Nxd4 exd4 8. Qxd4 with strong play on the kingside for the pawn; (b4) Nxf3 7. Qxf3 threatening mate on f7 while attacking the bishop as well; (b4) Bb6 7. Bb2 giving white fluidity on d4 and strong tension/ play. So maybe Nxd4 wasn't a good move after all?? If 5. ... exd4 6. b4 Bxb4 (seems better than Nxb4) 7. Nxd4 and this looks great for white-- I will place my dark-squared bishop on b2 and my other knight either on c3 or e2, followed with Re1 and wherever the queen fits in. If instead 5. ... Bxd4 6. Nxd4 Nxd4 and 7. f4 looks just fine. Please give your thoughts about this and reply/ respond if you see any error in my calculations. Thanks!