Pere Riba, crew chief to Jonathan Rea, believes improvements to Kawasaki's ZX-10R and a release of pressure are responsible for an impressive winter of testing, and feels the two-time World Superbike champion is approaching 2017 "in the best shape since the beginning" of their working relationship.

As he prepares his bid for a record third straight World Superbike title, Rea has been in ominous form throughout the winter months. The Northern Irishman topped the time sheets at every test he attended, which included a stunning performance at Jerez in November, when he outpaced every MotoGP machine present.

And while Riba feels his rider's recent speed is partly down to engine and chassis improvements to the Kawasaki, riding without the pressure that Rea carried while defending a sizeable world championship lead in the second half of 2016 is another key factor.

Speaking to Crash.net at Kawasaki's World Superbike team presentation in Barcelona on Thursday, Riba said, "I've known Johnny for many years and we've been working together for three years.

"I know his preferences. I know his needs for the bike. I know the feeling he needs to receive from the bike, set-up wise... Many, many things. There are also some points that impress me just how he is in this moment. I expected to keep growing, but the amount we are... I am a little impressed.

"In my opinion we made a step forward with the bike. We have different things in the engine. We work with more revs, a little more power. [We worked on] Different strategies with the electronics and we make a step. About the chassis, we made some small steps.

"About Johnny there are two points. He's understanding the limits of the bike and still growing. Another one that maybe he doesn't say, is that he won the first championship. The second one was much more difficult, because after the first he was quite pressured. This is normal.

"He won the second which was much more difficult than the first. We had a new bike. The package was not so easy. Anyway he managed and won. But when he won the second, he breathed out. And now, he's just going on the bike, like when he's going to do motocross, and enjoying. This is one extra.

"You put this together with the engine and chassis improving and boom! This is what happens. It's impressive. In the previous two years he was never the top, top, top. Jonathan was not a winter test rider. He's a Sunday racer. Now on the bike the lap time comes."

"He's not pushing, it's just coming. It's amazing. With a qualifying tyre, on long runs, lap times, he was first in Aragon, first in Jerez [in November], first in Jerez [at both tests in February] always. The whole package grows and he's enjoying. No pressure."

Riba's pleasant surprise at Rea's speed throughout the winter months has brought him to the conclusion that the 2017 series will ultimately come down to a scrap between his rider and Ducati's Chaz Davies.

"I believe we are in the best shape as a package since the beginning. On paper I feel Johnny is the most strong but racing is racing. We go to Phillip Island and we have to manage the races. This is the most important.

"Chaz is very strong and in my personal opinion, on paper, Chaz Davies and Jonathan Rea will be the guys fighting for the championship. That's my personal opinion."

While Rea eventually claimed his second title by 51 points, he repeatedly encountered transmission issues while downshifting throughout the year. It was one area his crew have sought to improve over this off-season.

"This is an issue that has been a pain in my ass," said Riba with a knowing smile. "This is two things together. One is technically, mechanically. The other one is the way Jonathan makes the action with the bike in some areas, naturally. It has created some problems.

"We worked a lot and we make some improvements this winter time. We made new parts and worked a lot. I hope, I believe that it will be solved. We'll see. This is how it is."