Backup team of the Cowboys (or any NFL team) would absolutely destroy Brady and a high school team.

How else do you define rockstar? Does being worth 100x the next guy not qualify? This is specifically relevant because football is a salary cap sport - every dollar on Brady is money not spent on someone else and therefore is a direct reflection of his measured value on the field.[0] As opposed to euro-football or older F1, where budgets are more flexible.

To your question: You can always saddle a 'rockstar' with enough negative-value players to result in poor overall performance. You've contriving an irrelevant situation -- also one where you've put 53 rockstars,[1] against a bunch of highschoolers plus one rockstar. Just about every player on the Dallas cowboys, except maybe the kicker/punter would drag an average highschool to the state championship.

[0]And we all know how that has turned out over the last 20 odd years.

[1]Rockstar-ship is situational/relative - the backup RB on the cowboys is a scrub in the NFL. He would also be the best highdchool player in the country by a large margin (aka a rockstar).