Nico Rosberg topped the timesheets on Saturday morning as rain disrupted the penultimate day of this week's Formula 1 test at Barcelona in Spain.
Although the day started off dry, and Rosberg was able to complete a series of low fuel short runs to set a best time of 1m20.686s on his final effort, everyone's programme at Barcelona was hit as rain soaked the track shortly before 11am.
Rosberg's short runs offered the first glimpse of the ultimate pace of his Mercedes GP car, with the team having so far limited its running to longer stints during this week's preparations.
The 1m20.686s was just a few hundredths slower than Fernando Alonso's benchmark effort for Ferrari from Friday, when he set a best lap of 1m20.637s during his low fuel runs prior to focusing on a race simulation.
Rosberg switched his programme onto longer runs once it became clear that track conditions would not improve.
All the best times of the morning were set before the rain fell, with second fastest Sebastien Buemi in the Scuderia Toro Rosso laying down his 1m21.413s during morning qualifying simulation work.
Adrian Sutil was third fastest for Force India with a best time of 1m22.951s, ahead of Felipe Massa in the Ferrari and Rubens Barrichello in the Williams - who spun off in the wet at Turn 5 at one point in the tricky damp conditions.
Both Jarno Trulli and Kamui Kobayashi worked their way through race simulation work, despite the damp conditions, while Jenson Button had a frustrating morning - stopping on track on his installation lap with the updated McLaren and then not running when the track was at its best.
Neither Timo Glock nor Sebastian Vettel completed flying laps as the conditions hit their programmes too.
Pos Driver Team Time Gap Laps 1. Nico Rosberg Mercedes 1m20.686s 56 2. Sebastien Buemi Toro Rosso 1m21.413s + 0.727s 21 3. Adrian Sutil Force India 1m22.951s + 2.265s 22 4. Felipe Massa Ferrari 1m23.490s + 2.804s 37 5. Rubens Barrichello Williams 1m23.976s + 3.290s 40 6. Jarno Trulli Lotus 1m25.059s + 4.373s 61 7. Kamui Kobayashi Sauber 1m26.216s + 5.530s 77 8. Vitaly Petrov Renault 1m26.346s + 5.660s 23 9. Jenson Button McLaren 1m36.667s + 15.981s 21 All timing unofficial