It appears as though we may have a cheater in my Online Dynasty league. As Hawaii the player struggles against human opponents but is blowing out computer teams. The only explanation I can find is that he is using 1 button mode in these games. Is is possible to turn off one button mode in Single Player vs CPU games in online Dynasty.
To the best of my knowledge, there isn't a way to turn it off. However, one-button mode shouldn't allow him to automatically dominate CPU teams. When playing against human opponents, there are plenty of other factors that can cause problems including online lag, a smarter opponent, and more varied play selection.
In my dynasty, it's common for players to obliterate CPU opponents but have defensive battles against human opponents. The input timing of offline vs. online play can be wildly different, and if he has a less-than-optimal internet connection he may be having a really hard time adjusting to the timing differences.
If you still feel that he's cheating, however, he may have been using the backwards pump fake glitch against the CPU. This glitch caused the entire defense (including the seconday) to blitz momentarily, leaving receivers wide open down field. See if he had uploaded any highlights of long touchdowns to the dynasty site - it will be blatant in the highlight if he was using the glitch.