There's basically 2 main ways to answer the Scotch after 3. ... - exd4 and then 4.Nxd4
First option: 4. ... - Bc5 Play might continue : 5.Be3 Qf6 6. c3 Nce7 7. Bc4 Ne5
Second option: 4. ... - Nf6 5. Nxc6 - bxc6. And now two continuations might occur:
6. e5 where the position is sharp
6. Nc3 and then 6. ... - Bb4 is more reliable for someone unprepared.
Can anyone tell me the best defense for the Scotch Defense? I lost 2 games in the last tournament playing it.