Lewis Hamilton trails Nico Rosberg as Jenson Button taken to hospital at German Grand Prix
Lewis Hamilton trailed team-mate Nico Rosberg as Mercedes dominated the second practice session at the German Grand Prix.
Hamilton was 0.394 seconds adrift of the German after a messy lap simulating qualifying and 0.2secs clear of Ferrari's Sebastian Vettel in third.
Red Bull's Max Verstappen and Daniel Ricciardo were fourth and fifth ahead of Kimi Raikkonen's Ferrari.
Jenson Button was eighth but was taken to hospital with an eye "irritation".
The 2009 world champion went to Mannheim hospital "to have a precautionary check-up", but later said on social media: "On my way back to Hockenheim from the Mannheim hospital for an eye examination, foreign body found & removed. All good for tomorrow."
Button had also complained of an overheating cockpit earlier in the session.
The Briton's team-mate Fernando Alonso, whose 35th birthday is on Friday, was 10th fastest, 0.138secs adrift of Button. The Spaniard also seemed to be unhappy with the car and had an untidy lap.
Hamilton appears out of sorts
Hamilton appeared to be on the back foot throughout the day, lagging a couple of tenths of a second behind Rosberg in the first session, on the qualifying simulation runs and on both the super-soft and soft tyres on the race-simulation runs.
But it turned out that Mercedes had warned him to take it relatively easy through Turn One after he received some warnings from race control about exceeding track limits.
The team did not want him to risk receiving a reprimand because he has already had two this season and a third would mean an automatic 10-place grid penalty.
That means his lap times are not fully representative of his potential performance.
Hamilton took the lead for the first time with his victory in Hungary last weekend, his fifth in six races - a run which has turned a 43-point lead for Rosberg into a six-point lead for Hamilton.
Red Bull and Ferrari set for collision course
Ferrari and Red Bull look set for another close fight for best of the rest, with Vettel and Raikkonen sandwiching the two Red Bulls, with Verstappen only 0.034secs quicker than Ricciardo.
Behind the Red Bulls, Force India and McLaren look closely matched, with Nico Hulkenberg setting seventh fastest time, ahead of Button and the German's team-mate Sergio Perez ahead of Alonso in ninth.
Williams had a disappointing day but can be expected to join that fight over the weekend.