Formula 1 returnee Nico Hulkenberg surprised at the start in Bahrain and finished the first day of practice in fifth place.
After the second session, the successor to Mick Schumacher, who had retired from Haas, was just 0.469 seconds slower than top man Fernando Alonso in the Aston Martin on his fastest lap (1:30.907 minutes).
The Spanish replacement for Sebastian Vettel, who retired at the end of last season, showed that the English racing team has made an enormous leap in development over the winter. Alonso's teammate Lance Stroll, who had surgery on his right wrist just a few days ago, finished sixth.
World champion Max Verstappen in the Red Bull finished the first day only a hair's breadth second (0.169 seconds). His teammate Sergio Perez (0.171 seconds), who had set the fastest time in the first practice session, landed directly behind him.
Formula 1 starts its 74th season with the Bahrain Grand Prix on Sunday (4:00 p.m. CET/Sky). Verstappen is aiming for his third world title in a row.