Red Bull KTM team manager Mike Leitner has explained why the factory reluctantly decided to replace Johann Zarco for the remaining rounds of the 2019 MotoGP season.

KTM had already agreed to release the Frenchman from the second year of his contract after an emotional meeting in Austria last month.

Zarco still intended to see out this season, but given his unhappiness and lack of feeling with the RC16, issues such as rider safety prompted KTM to put Mika Kallio on the Frenchman's machine for the last six rounds.

The Finn will effectively be taking part in an audition for the 2020 race seat, with Leitner confirming Kallio currently has the 'highest chance' of being Pol Espargaro's team-mate next season.

"We started working with Johann after Valencia last year and from the first moment he couldn’t really build-up a good feeling on our bike," Leitner began.

"From the technical side we tried many things to give him a better feeling. We pushed hard and had some highlights, then again it was not so good, while on the other hand Pol performed better, better, better.

"Also when Dani [Pedrosa] came in we tried to understand what feeling is really missing for Johann to perform better on our bike. And to be fair, Johann tried to get better and we tried to help him.

"Then in Spielberg on Saturday evening Johann came to us, Pit [Beirer] and me, and told us clearly, 'I will not do two seasons with you guys because I don’t have the feeling, I can't ride my style'.

"When a rider tells you 'I don’t want to ride with the bike', it goes to the point where you also have to think of rider safety and danger because the riders are risking a lot.

"For sure KTM is not a company that will force a rider to do things on a bike that maybe he doesn't like.

"He had another big crash during warm-up at Misano, he was very lucky not to hurt himself. So you start thinking 'is this is the correct way?' When he had already decided to stop this project, to push him for another six races to go to the limit.

"So we decided for the project and for the future it's better to bring in Mika... The decision was done very fast after Misano."

Zarco's initial reaction to the news had been one of shock.

"Everybody can feel for him as a sportsman and a person," Leitner said. "Nobody in this project is happy that we have to move to this point.

"We know he's a great rider, that's why we contracted him. He's a talent and a passionate MotoGP rider. But when you see that really the rider is not connecting 100% to the project, it is also a relief.

"To see a rider on your bike who is not completely motivated or happy is not so nice to watch. I think at the end this is the result of that.

"Everybody knows that when a rider is not happy with the bike it's a hard job for them. It's not funny when you want in your mind to race for a top-five position and you cannot achieve it.

"On the other hand, our project is so young and what we've achieved in two and half seasons is not so bad. So this was maybe a point where Johann was struggling, because his expectation was maybe much higher.

"And of course to hear [him say] constantly in the press that the bike is bad, and then stopping the contract in Speilberg and we can see he's not happy. So what future?

"There are many people involved in this project and it's a big investment, so the decision was to stop it now."

Leitner revealed that, prior to Zarco calling the Red Bull Ring meeting, the team were still confident he could be successful with the RC16.

"We knew it would be very difficult, but we also know what we will do for the future development of the bike. What will be coming in four months, six months, eight months…. We are working hard and maybe [these developments] could even help him.

"The most important thing in the project is the rider and when the rider is motivated you can move many things. But if the most important person is not motivated or wants to stop, then there is no meaning to continue."

Development of the bike was also a factor in Zarco, who finished eleventh at last Sunday's Misano race, being dropped.

"This project is going forward and you have a rider in the team who will leave at the end of the season and go to a competitor," Leitner said. "So it blocks you in a way - future developments, new parts, ideas for where the project will go.

"This was also why Mika, with the project since we started in 2016, is a great option to put on the bike. We know he is 100% behind the project, knows the history and looking forward to working with him."

The other reason is that Kallio now looks the best choice to replace Zarco in 2020.

"Mika is back also because Mika is one of the candidates to ride a full season in 2020," Leitner confirmed.

"At the moment we don’t put names on the table but the highest chance at the moment for 2020 would be Mika. Because after 2020 all the contracts for the next two years start and all the riders are open for teams."

Although Kallio has now recovered from the serious knee injury at Sachsenring 2018, Leitner is aware "it's not easy to jump in after 13 rounds and go racing with these boys. So we need patience and give him time to come back to race speed.

"But we will also see how he will perform and this helps us in the [rider] decision for the future, that's clear."

While Kallio will either be testing or racing for KTM next season, Zarco's future is less clear.

The double Moto2 champion has no intention to retire and is seeking a test-riding deal or at least a place in Moto2 to put him in the shop window for a 2021 MotoGP comeback.

Zarco will remain under contract (and being paid) until the end of the year, but Leitner said KTM would not stand in Zarco's way if an opportunity, for example as a replacement rider, arises before his contract expires.

"We will not block his career," Leitner said. "This is clear, this is not the idea of KTM to do anything bad.

"It just didn’t work out with us. But we had a good conversation, I had a long talk today with him also and I respect him as a rider and a person. I think all the company feels like that.

"Whenever he shows up and has an option [with another manufacturer] we would be very open to talk with him about that."

Zarco claimed KTM's first MotoGP front-row during a damp qualifying at Brno and took a best race finish of tenth in Catalunya.

However, his 17th place in the world championship (27 points) compares with eleventh for Espargaro (77 points) and sixth overall during both seasons at Tech3 Yamaha, when Zarco celebrated six podiums and came the closest yet (+0.251s) to winning on a satellite M1.

"We worked a lot on the chassis side and set-up. Many, many things. It is not that nothing helped him. It was just not enough for him, it looks like, that is why he made this decision," said Leitner.

"But I think he was [improving with the KTM]. He did a not-so-bad qualifying at Misano and the race was acceptable.

"Johann for sure is not a bad person. He is not a bad rider and everything. But somehow he did not get connected to the feeling on the bike."

Does the Zarco experience change how KTM will approach future rider signings?

"I think you only know when the rider is on the bike," he said. "There are always in history riders that cannot connect to a certain brand. It's an experience we’ve had now with Johann, but other manufacturers had similar problems before.

"It's a part of racing I think, you have to choose your rider and sometimes [it doesn't work]."