Lando Norris has outscored his teammate at all of the past five grands prix.
The McLaren driver edged out fellow driver and championship contender the Australian for the top spot in the dying seconds of practice at the Sao Paulo Grand Prix.
Norris, who seized the points lead from Piastri by one point after his victory in Mexico City two weeks ago, topped the Melbourne-born driver by a mere 0.023s.
Before then, Piastri had been the quickest of the McLaren pair during the running before sprint qualifying set to begin at 18:30 GMT.
Max Verstappen, the other racer in the championship fight, sitting with a 36-point deficit Norris, ended up in 17th position as his Red Bull team followed a different programme.
His teammate the Japanese driver was the sole competitor to go off, if briefly, when he spun at corner four soon after starting.
Tsunoda spun out over the exit kerbs before sliding over the escape zone, and was lucky to get away with just a slight brush of the fence.
The Ferrari of the seven-time champion also spun, at the very end of the practice, turning around through the high-speed Mergulho corner approaching the last turn on to the start-finish straight.
Hamilton finished practice in P19, trailing teammate the Monegasque driver.
Norris and Piastri were far ahead of the remaining drivers, with Nico Hulkenberg's car in third, 0.619secs off Piastri's best.
Aston Martin's the Spanish driver was fourth fastest, with the Sauber of Gabriel Bortoleto fifth from the Mercedes of George Russell and Alpine's Pierre Gasly and Williams' Sainz.
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