Piastri had looked to be struggling compared with Norris since the start of practice and was a good chunk off the Briton in all three qualifying sessions.
Norris said: “Disappointed not to be on pole but not a surprise for us to be just a bit slower than the Red Bull lately.
“A little couple of bits here and there I could have improved on and caught a few bumps a little bit wrong, that’s the difficulty of this track. Otherwise, all happy.”
Piastri said: “A pretty scruffy lap. Just didn’t really get it together. In some ways, I feel a bit fortunate to be third. The pace in the car is good. It’s nothing major, just been a bit of a messy lap and hopefully I can tidy it up tomorrow.”
The sprint offers eight points for the winner down to one for eighth place.
The stand-out performance in qualifying came from Hulkenberg, the first time he has qualified in the top 10 all year, and the best Sauber performance of the season.
Their previous top grid position was seventh for team-mate Gabriel Bortoleto in Hungary at the start of August.
“Satisfied, happy, as you might imagine,” the German said. “P1 looked too good to be true. We weren’t sure if it was the real deal but we were able to continue that trend. Hopefully we can hang on to it this weekend.
“The pace was just there. The car seemed to be fast and in a good window, hit the sweet spot, I think that’s all.”