It's true that flukey things happen in this game. I've had Randy Johnson post an ERA of over 6 in a RT league when he was having one of his best years.
That said, if the game were totally predictable based on stats, there wouldn't be much point in playing the games.
Over time, the flukes balance out and the game seems to have the "feel" of managing a realt team.
If you think flukes don't happen from small samples, look at the standings: Tampa Bay is tied for first in their division and Detroit leads theirs.

Dave N