With his MotoGP lead whittled down to a single point, Valentino Rossi responded by leading opening practice for the first time in 2015.
The Italian was later pushed to third by the Repsol Hondas of Dani Pedrosa and Marc Marquez in the afternoon session at Assen, but remained three places clear of team-mate and title rival Jorge Lorenzo.
Rossi's mood was raised further by the performance of the new Yamaha chassis and - after a back-to-back test on Thursday - The Doctor intends to switch both his M1s to the latest frame on Friday.
“I'm very happy and satisfied about this first day,” began Rossi, who was only 0.202s behind Pedrosa. “It was an important day, especially because of the weather, and you have to use this dry time to the maximum because you never know about the weather at Assen
“We had the chance to understand about the new chassis from the test in Aragon. I'm happy because already from this morning when I put the new chassis I improved my lap time, my pace and I felt good with the bike.
“We continued this afternoon and concentrated more on the bike with the new chassis and we had the chance also with the 40-degree asphalt to try the harder tyre that could be an option on the rear for the race.
“At the end I put the medium tyre and I did some very good lap times, also with the pace I'm not so bad. So in general it is a positive day.”
Pressed on why he prefers the new chassis, Rossi replied: “The bike is more easy to ride. It is like it is lighter, better agility and especially it looks like the tyre has better grip. Especially after 20 laps. So I like.
“It is also important to try a chassis in different tracks and conditions. We had tried it only at Aragon so it is very positive that it is good also at Assen. The only negative is maybe in braking, a little bit more unstable, but I'm not sure. [Overall] it is a small improvement I think.
“Today we did a back-to-back test between the new and old chassis. Tomorrow I think we will use two new chassis. With two bikes we will have more chance to make small modifications during practice.”
Rossi arrives at Assen looking to halt Lorenzo's faultless run of four successive wins, during which the Spaniard has led every race lap.
“We are both in good shape,” said Rossi. “We are very strong. Especially Jorge was impressive in the last races. But at the same time I was good. I ride well and I stay always on the podium. This is very important for the points.
“For me it is also very important to understand the level of the other bikes because in the last three races, twice we finished 1-2 for Yamaha.
“But I'm worried especially about the Honda because it is impossible that Honda continue like this. So it is just a question of time until they recover the gap, but we hope that we remain more competitive, especially in the races.”
Reigning double champion Marquez, whose three non-scores have left his 2015 title hopes in tatters, has switched back to last year's chassis for Assen.
“[Marquez] has the old chassis and both riders - Marquez but also Pedrosa - are very fast, very strong. So it's good to stay with them, be in third position and only a small difference from first,” Rossi added.
Asked what he would do if he found himself in a close second place behind Lorenzo heading into the last chicane on Saturday, Rossi replied:
“It is difficult to say because it depends on the feeling you have in the race. For sure if we have the feeling that you are good in braking and you can attack, you can try. But at the same time you don't have to risk too much if you don't feel it is possible.”
The unique Saturday race for Assen means final practice and qualifying takes place on Friday.