Verstappen, seeking his fifth consecutive drivers' championship, said: "Pretty OK. I was fairly happy with the car; we just need to be probably a little bit faster. We are still not quick enough but we have been in a decent window.
"It seems like it's a decent gap we need to close but we will just try to put the best car forwards and let's see how much we can find overnight. Single lap and long run needs to be better."
Piastri, who sat out the first session as McLaren IndyCar driver Pato O'Ward fulfilled one of the team's obligatory young driver test sessions, was not quite in the same ballpark as his rivals.
"I got there pretty well on the medium (tyre) but on the softs didn't get the most out of the grip on that first timed lap.
"Finding my feet but clearly some things to try and improve for tomorrow. But after just one session, not too bad. The car feels like it's in a pretty decent place. Some small tweaks of course, didn't feel perfect out there but nothing major.
"The car's looked quick. Just need to get some more laps under my belt and find my feet a bit more."
On headline times, Mercedes' George Russell was third fastest, from Haas driver Oliver Bearman, who said over the radio that he could not believe just how good the car was feeling.
Nico Hulkenberg and Gabriel Bortoleto were fifth and sixth in Sauber's final race before they morph into Audi for the German manufacturer's debut season in F1.
Racing Bulls' Isack Hadjar was seventh in his final race before his promotion to Red Bull in 2026, followed by Ferrari's Charles Leclerc, Aston Martin's Fernando Alonso and the second Mercedes of Kimi Antonelli.
Ferrari's Lewis Hamilton was 14th.