During a busy session which saw all three tyre compounds used, Rosberg was first of the Mercedes drivers to set a time on the supersoft tyre and duly went over a second quicker than the 2014 pole position time with a 1:15.517. Hamilton's response was 0.326s slower than his team-mate, although still over 0.8s clear of Sebastian Vettel in third.
Vettel and Kimi Raikkonen ensured Ferrari finished ahead of Red Bull at the end of the session, with Max Verstappen fifth and Daniel Ricciardo sixth. While the two teams were closely matched, they also had Fernando Alonso for company in seventh as 0.3s separated all five cars.
Jenson Button was 0.4s slower than his team-mate in eighth place ahead of the Toro Rosso pair of Daniil Kvyat and Carlos Sainz. The top ten all set their best times on supersoft tyres, with the Williams pair of Valtteri Bottas and Felipe Massa - 12th and 13th respectively - the first two in the standings to post on the softs.
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Bottas also had a spin during the session as his Williams swapped ends at the Turn 6 hairpin, with Bottas having to quickly recover before a Mercedes came through the same corner.
Another driver to set a time on the soft tyre but also have an off-track moment was Romain Grosjean, who endured a tricky session. The Frenchman had already complained of problems with traffic after encountering a very slow Kimi Raikkonen in the stadium section when he slid off track at Turn 8. Grosjean damaged his tyres and left gravel on the circuit after rejoining with just two minutes remaining on the clock.
While the majority of teams have just one set of medium compound tyres available this weekend, both Force Indias have three sets and opted to complete all of their running on the mediums in the opening session, resulting in the two cars finishing 15th and 16th.
Charles Leclerc enjoyed a strong outing for Haas, with the Monegasque driver finishing 17th, within 0.3s of team-mate Grosjean. Esteban Ocon was the other FP1 replacement driver to take part in the session, recovering from an off-track moment at Turn 4 to end up just 0.048s slower than Kevin Magnussen in the lead Renault.
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