Lando Norris has outscored his teammate at all of the previous five race weekends.
Lando Norris just pipped fellow driver and title rival the Australian for the fastest time in the closing stages of the practice session at the Sao Paulo Grand Prix.
The British racer, who seized the title advantage from his teammate by a single point after winning in the Mexican Grand Prix recently, topped the Melbourne-born driver by a mere 0.023s.
Before then, Piastri had been the leading McLaren for most of the session before the sprint shootout scheduled for 6:30 PM GMT.
The Red Bull star, the sole remaining contender in realistic title contention, sitting 36 points behind Norris, finished in 17th position as his team ran a different programme.
His teammate the Japanese driver was the only driver to go off, if briefly, when he rotated at the fourth corner during the early running.
The Japanese slid over the curbs on exit before spinning across the run-off area, and was blessed to escape with just a light touch of the wall.
Ferrari's the seven-time champion also lost it, at the very end of the session, turning around through the quick descending corner approaching the last turn on to the pit straight.
The veteran wrapped up in 19th, one place behind team-mate Charles Leclerc.
The McLaren drivers were significantly quicker of the rest of the field, with the German's Sauber P3, 0.619secs slower than Piastri's best.
Aston Martin's the Spanish driver was fourth quickest, with Sauber's Gabriel Bortoleto in front of Mercedes' George Russell and Alpine's Gasly and Williams' Carlos Sainz.