Some may already know this, but I haven't seen it discussed and I just discovered it today.

All but one of my players have skill levels of 70 /70 /69.8 (or equivalent variations)
The other player is a 76 /76 /72.8 scout.

So, I was expecting my team average quality to be 69.8 or 70, but it shows as 69.2 ...the average of 69*21 + 74.

Interesting. So my team quality is shown as nearly a point low. Not that a single point means much.

Now, indulging in some speculation: some people have tried to manipulate their cup draw by lowering team quality until after the draw, but reported a lack of success.
What I hypothesise, is that the cup draw is a combination of TWO factors.
One is based on your team average quality (or average of the top x players) - call this Cup quality
The second factor is your previous season league finish.

So, for example, all the teams with a CUP quality of, say, 65-75 are tossed in a pool together. THEN these teams are subdivided according to league finish. So all the teams within this CUP quality pool who finished in the top 4 in their league would form a sub-pool, and all the teams who finished 5th - 8th would form another sub-pool, etc.

And unapplied skill points do NOT seem to count towards your CUP quality.

Note that the specific numbers used in this hypothesis are just for example of the broader idea, (e.g. i actually see teams that finished as high as fifth in the same cup with those who finished as low as 10th)