Not enough.
Case 1, +15 stars with all players, case 2, +16, really the situation is generally+1 and then, count, the game never select all players, there's an scenario, scenario can depend for example of the position of the teams in the classification. Then 1 good player with a good day can kill the game, or test and have a the correct man in fouls/corners can make the differance... and more things..
34 seasons looking matches tells me that if you want a guarantee 90%... maybe the line starts in +3 stars... and we can see more matches and the conclusion probably will be more radical...LOL