Ben Spies set the pace in the second practice session for the Dutch TT at Assen with the fastest time of the day in 1m34.866s.
The under-fire American, who scored his maiden grand prix victory at the venue 12 months ago, was in the hunt for much of the second half of the 45-minute session and just edged out Cal Crutchlow in the final stages.
Spies and the Tech 3 Yamaha rider were split in the end by just 0.006s, while the first 11 riders were all covered by less than 0.5s.
Championship leader Jorge Lorenzo looked unruffled in fifth, just 0.191s off the pace, having been at the sharp end for much of the session as he worked through long runs, while Honda's Dani Pedrosa (sixth) also spent a period of time at the top of the list.
Andrea Dovizioso was seventh fastest for Tech 3 ahead of Valentino Rossi, who was more than 0.3s off his Ducati team-mate Hayden.
Hector Barbera was ninth, the Spaniard recovering from a fall at Turn 10 when the front-end of his Pramac Ducati washed away inside the first five minutes of the session.
World champion Casey Stoner could only manage 10th place, the Honda rider spending much of the session evaluating different Brigestones and making repeated trips to his pit garage.
1. Ben Spies 1m 34.866s
2. Cal Crutchlow 1m 34.872s
3. Nicky Hayden 1m 34.968s
4. Alvaro Bautista 1m 35.008s
5. Jorge Lorenzo 1m 35.057s
6. Dani Pedrosa 1m 35.080s
7. Andrea Dovizioso 1m 35.257s
8. Valentino Rossi 1m 35.296s
9. Hector Barbera 1m 35.298s
10. Casey Stoner 1m 35.304s