One of Uber’s original employees — and one of former CEO Travis Kalanick’s top boosters — is stepping down from his leadership role at Uber.

Ryan Graves — one of the company’s first employees, the first full-time CEO, and one of its biggest shareholders — said he will transition out of his operating role and remain on the board.

Nobody is taking over for Graves as Uber’s senior vice president of global operations, and there are no plans to fill the role immediately given all the other vacant executive positions, a source familiar with the matter told CNBC.

As a board member, Graves will still be involved in finding the replacement for his successor, Kalanick. While Graves and Kalanick have long been close, recent reports from The Information indicated that Graves’ ties with Kalanick might be unraveling.

Graves’ involvement in Uber’s recent scandals thrust him into the spotlight earlier this year.

In particular, Graves was aware of “greyballing,” a tool Uber used to evade authorities around the world, according to The New York Times. That program is now subject to a criminal probe, Reuters reported. An Uber insider told Business Insider that Graves, known as Uber’s “Mr. Nice Guy,” had “vanished from the office,” and that employees feel Graves hasn’t displayed the leadership they would have expected. Recode reports that Uber’s HR — accused by a former employee of dismissing sexism allegations — reported to Graves.

Graves, who was relatively inexperienced before his serendipitous start at Uber, has been key in launching Uber’s expansion into international markets and defining the company’s core values, like “super pumpedness.” He’s one of the executives that’s said to be leading the company, which is currently without a CEO.

He has been overseeing UberEverything (which includes UberEats and UberRUSH). Jason Droeg, head of Uber Everything, will continue to head it with his current title.

Early Uber investor Chris Sacca tweeted on Thursday that he was grateful Graves took a huge risk on Uber. When Graves started at Uber, Kalanick had been running the tiny San Francisco company on a temporary basis, dropping by 15 to 20 hours a week.

“His grind was relentless. Legendary. Uber was launched in zero cities when he joined and operates in over 600 cities worldwide today,” Sacca tweeted.

Tweet: Within the Uber boardroom, @ryangraves is the director most consistently respected by the others and is great at building consensus.

“There is another lesson I’ve learned that we should have applied much earlier,” Graves wrote in an email obtained by CNBC on Thursday. “We should have taken more time to reflect on our mistakes and make changes together. There always seemed to be another goal, another target, another business or city to launch.”

Here’s the full email that Graves sent to colleagues:

“Uber team —

In the past 7.5 years of building Uber, I’ve learned so many different lessons, one of which is the fact that people who embrace uncertainty and change have the best grip on reality. In the middle of September, I’ll be embracing another big change on my journey with Uber and will transition out of a full-time operating role to focus on my role as a Board Director.

In every position I’ve held at Uber, as GM, then CEO, then SVP of Global Operations, I’ve focused on people and team. Uber’s launch, our rapid growth, and now global impact, are all a testament to the quality of the folks that I have had the pleasure of working and growing with. That team is now the driving force behind the durability and importance of the business we run in over 600+ cities.

In some ways my focus going forward will not actually change very much — it remains all about people, and it’s clear to me the stability of our board of directors, the selection of our new CEO, and the empowerment of our management team is what is needed most. So I will do everything in my power to deliver on those goals for the benefit of our organization and the millions of people — riders, drivers, eaters and couriers — and their communities that Uber serves every day.

I could not possibly stress enough how insanely proud I am of this organization. The dedication towards our mission of providing transportation that can be trusted, to everyone, is noble. We, as a team, have achieved something that has truly changed the world for the better, and will continue to do so long into the future.

I also have deep gratitude for the lessons learned from Travis, from my colleagues on Uber’s ELT, and my Global Ops leadership team over the years — notably Rachel, Austin, Jo, Mac, Pierre, Droege, Penn, Jambu, Ro, Mike, Amit, Meghan, Barnes, and so many others who have given so much of their hearts and lives to building this company. Thank you. Without you, I wouldn’t be the person I am today and for that, I will forever be in your debt.

When you go through an experience like we have building Uber you forget that it’s not just the people across the desk that are making a huge investment, it’s also the partners and spouses, the families and the friends at home also making sacrifices. I would never have been able to make this journey without my wife Molly there to listen and advise. The ride hasn’t always been easy but nevertheless, she’s been there with me to laugh, to cry, to plan, and to celebrate. She deserves more credit than anyone in supporting me through it all. She’s been the most constant and enduring partner, right at my side, and building her own company and our family along the way. I *really* look forward to being able to return the love and spend more time with her and with our boys.

So, why now? Well, there is no great time for a move like this one. But it’s really important to me that this transition doesn’t take away from the importance of the onboarding process of our new CEO, whoever they might be. My hope is that ensuring my transition is known and planned for well before our board’s decision on CEO it will help to make it clear to our team and to our new leader that I will be there to support however I can.

There is another lesson I’ve learned that we should have applied much earlier. We should have taken more time to reflect on our mistakes and make changes together. There always seemed to be another goal, another target, another business or city to launch. Confucius said that reflection is the noblest method to learn wisdom, and fortunately, our new found reflection and introspection has become an asset to us and we have evolved and grown considerably. Our culture, our processes, our leaders, and our teams have become wiser, stronger, and more mature because of it. Regardless of which role I hold in the future, I’ll be dedicated to supporting Uber’s leadership, partnering with Uber’s new CEO to understand the complexities of this business and this organization, and to continuing to deliver on the critically important mission and future we have ahead of us. Again, thank you all, and let’s Uber on!

Best,

RG”