I'm having the same problem actually. It seems that the momentum slider favors the computer. Once they score, they score a bunch within few minutes. I haven't won a game yet on NHL 14 (about 5-7 played so far) and I've had 3 or 4 blowout losses. (by the scores of 8-2, 7-2 (twice))
Last game I played I thought it was actually gonna be a hard fought game, scoreless into 3rd. Next thing u know they score 3 quick goals to win it pretty much. I scored one but that was all I could do. So when they do that, it makes the game feel like a wasted one after a couple good periods.
This game is probably the first NHL game I couldn't care less to play with, been going back to my The Show games.