Espargaro tops practice at Argentina's happy hunting ground
The Spanish rider edged out teammate and 2017 Argentine race winner Maverick Vinales by 0.162sec with Ducati's Marco Bezzecchi in third spot.
Ducati, who have never won at the Termas de Rio Hondo circuit, filled out the next four spots with world champion Francesco Bagnaia down in sixth place, 0.426sec off the pace.
Bagnaia won the season-opener in Portugal last weekend, taking maximum points from the inaugural Saturday sprint race and Sunday's showpiece event.
The top 10 in Friday's practice go straight into the second qualifying run on Saturday.
Yamaha's Fabio Quartararo, the 2021 world champion, 2020 series winner Joan Mir, on a Honda, as well as KTM's factory riders Jack Miller and Brad Binder, all missed out on the top 10.
They will instead have to compete in the opening qualifying session on Saturday.
Four riders are missing the Argentina Grand Prix having suffered injuries at a chaotic season-opener in Portugal.
Bagnaia's Ducati factory teammate Enea Bastianini has a broken shoulder blade.
Spanish veteran Pol Espargaro is facing a lengthy absence due to a bruised lung and fractures to his jaw and spine following a crash in practice.
Six-time premier class champion Marc Marquez is out after undergoing a fifth surgery in less than three years following his spectacular collision with Aprilia rider Miguel Oliveira.
The luckless Oliveira is also sidelined due to a leg injury sustained in that accident, leaving Sunday's grid in Argentina reduced to 18 from 22.
Earlier Friday, it was announced that Germany's Jonas Folger will replace Pol Espargaro at the GasGas team from next month's Grand Prix of the Americas.
