Sebastian Vettel could make the most of warm temperatures on Sunday in Bahrain to gain sole possession of the Formula One championship lead again in what promises an exciting title duel with Lewis Hamilton.
The Brit led from start to finish as he served a reminder of Mercedes' speed to Ferrari's Sebastian Vettel, victor of the first race of the season in Australia.
Bottas, who concentrated on long runs for much of the session, was down in 15 place and 2.305s off the pace. With stiff competition between the two drivers and teams, the question still stands.
Team-mate Fernando Alonso, who it was announced on Wednesday would miss the Monaco Grand Prix to race in the Indianapolis 500, was eighth fastest, 1.675secs behind Vettel, setting his time shortly after Vandoorne's problem. Red Bull will hope to get back into contention sooner rather than later, but are unlikely to do so this weekend.
The drivers will take to the track for the second time later in the day.
The second session, which started at 6 p.m. local time (1500 GMT) was in considerably cooler temperatures and closer to the conditions expected in Saturday's qualifying, which comes after a third practice run. Live text commentary, leaderboard and imagery on BBC Sport website and app.
Live coverage of the second practice session starts at 4pm BST.
Following the two races, the pair are levelled on points in the drivers' championship and Wolff believes that pattern would continue to develop as the season progresses. The two drivers are preparing for one of the closest title battles witnessed in recent seasons and look to be in a league of their own. Hamilton won the pole, but after Rosberg managed to jump him on the way into turn 1, things went from bad to worse for Hamilton as his future teammate, Valtteri Bottas, speared into the side of him, dropping him well down the order. He is now fourth in the F1 standings after taking third in the first race and sixth in the second.
Force India driver Esteban Ocon continued his good start to the season and recorded his second consecutive points scoring finish after he again grabbed the final point at the Shanghai global circuit.
Pascal Wehrlein has received ample criticism for missing the last two races through a lack of fitness following his spectacular crash at the Race of Champions exhibition event in January.
FILE - This is a Sunday, April 9, 2017 file photo of Mercedes driver Lewis Hamilton of Britain as he tosses his trophy into the air on the podium after winning the Chinese Formula One Grand Prix at the Shanghai International Circuit in Shanghai, China.
Red Bull Racing (37 points) are in third place but are already falling behind. The vehicle was strong on Sunday, I think Lewis had a very strong race all the way through, there was no tough battle for the win, so as a team we should have been able to finish one-two.