for simulated CPU vs CPU matches, the game engine in TE2013 calculates a form of the day for each player based on their Consistency & Concentration skills and a random value, and depending on the result it may apply a handicap or bonus of a few percents on their skills.
In TEM2, this behavior is also done for the real-time matches, as it's a manager game and thus it makes sense.
However, for TE4, I wonder if I should let this feature plugged in or not.
The main downside is that it could let you beat the best players when they have a bad day (although it should be pretty rare, as it's mostly the low ranked players who have bad days), and thus telling "I beat Federer in 2006" could be less impressive. (I'd display the form of the day in the Player Stats, so you can check what's going on in each match)
On the other hand, it's more realistic, and for a few players which are pretty unstable, it'd paint them more accurately (especially as 10% of bad days are changed into good days

So what do yo think ?