Piastri was second fastest in Free Practice 2, just under two-tenths shy of pace-setter Charles Leclerc.
The Australian had a largely uneventful day, in stark contrast to the scrappy sessions endured by Max Verstappen.
“Honestly, it’s been an encouraging day for us,” Piastri said.
“I think the pace has been good in both the qualifying runs and the race runs.
“Yeah, feeling pretty happy.”
Piastri this weekend has the full complement of upgrades debuted in Miami.
There, the Australian had only half the package but this weekend is running the same spec McLaren as his team-mate, Lando Norris.
“I felt pretty comfy with the car from the moment we got on track,” Piastri said.
“I think just try and find a bit more overnight and see what we’ve got.”
Piastri proved the closest challenger for Max Verstappen in the opening stages of the Miami Grand Prix two weeks ago before an ill-timed Safety Car favoured his team-mate.
Norris went on to win the race as McLaren underscored its credentials as a serious contender at the front of the pack.
Exactly where it sits this weekend, however, is unclear.
None of the 10 teams debuted upgrades, clouding opening practice as they spent time assessing their new parts.
A scrappy day from Red Bull Racing also masked its performance, leaving both Verstappen and Sergio Perez down the order.
Mercedes also seemed somewhere on par with Ferrari, suggesting McLaren will face stiff opposition to repeat its Miami success.
“It’s very tight out there,” Piastri observed.
“Red Bull have looked a bit up and down, which is a bit unusual for them.
“Ferrari, Mercedes looked quick as well at points, but I definitely think we’re in the fight.
“But I think where we were today is not unrealistic.”