Well, Tiafoe has already had positive H2H with Fritz, I think it is 2-0 or 3-0 at junior level. Fritz apparently was under pressure as favourite for the win, big stage... he was rushing on many balls. First two sets were identical, with losers of them committing many errors, low serve percentage. But nevertheless, there were some great flashes from both.
Zverev definitely has tough task, and he'll need to step up in order to win.
The race is not over, though I am afraid Lisicki will definitely miss Rio. Upcoming period of year is not the one Sabine fancies the most.