Kiwi Formula One driver Brendon Hartley has taken to social media following his bitter exit from the Toro Rosso team, yet his former employer has given no official acknowledgment of his contribution - or even his axing.

Hartley was sacked by the team on Tuesday when Toro Rosso announced Alexander Albon, who finished third in Formula Two this year, would be the new driver to team up with Daniil Kvyat for the 2019 season.

With Hartley's 2018 teammate Pierre Gasly promoted to the Red Bull Formula One team there seemed a chance the Le Mans winner and World Endurance champion would race for a second full season.

But after finishing the season in 19th on the drivers' championship standings out of 20 drivers with just four points and a ninth-placed finish at the US Grand Prix his best of the season, the 29-year-old's departure wasn't a huge surprise.

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"I left the circuit on Sunday with my head held high," Hartley posted on Twitter.

"I'm very proud of my story and journey so far but I am left feeling I have unfinished business in F1. For the moment that has been put on hold. I've hit speeds bumps before and I am a strong believer that though situations make you stronger. It also helps that I have a great NZ support crew, family, friends and wife.

"I also want to thank my trainer Rich and almost all of the 500 strong Toro Rosso staff who I have enjoyed working with this season, all of the engineering team, the mechanics, marketing, PR, logistics, hospitality crew, factory staff and of course at Honda Racing.

"I really do appreciate the support I have received from fans across the globe this year, I still have plenty more pages to write in my story and will make the most of the opportunity's in the next chapter."

Toro Rosso's handling of Hartley's departure seems on par with the team's performance in Formula One this season. No mention has been made of the Kiwi's exit on the official Toro Rosso website with his profile quickly removed.

However Honda motorsports boss Masahasi Yamamoto praised Hartley's time at the team.

"On behalf of Honda, I would like to express my thanks to Brendon for all his hard work this year," Honda's Yamamoto said.

"Brendon is always a friendly and charming person who immediately embraced Japanese culture and Honda's way. It gave everyone at Honda so much power and confidence in what we were doing this year after several difficult seasons.

"I particularly remember when he qualified sixth at our home race in Suzuka. That meant a lot to Honda.

"We will miss him and wish him all the best for the future."

According to motorsport journalist Bob McMurray, Hartley's performance simply wasn't good enough and the Kiwi driver's only shot at staying in Formula One was to be a test driver.

"All the seats are filled now for this coming season, every seat is effectively spoken for, so there's not going to be any seats in Formula One," McMurray told Radio Sport.

"The best he can hope for is to pick up as a third driver, a test driver role with a team.

"He could have performed better, it's that simple really. I'm not being down on Brendon, I think he's a fantastic driver, but he simply could have beaten Gasly.

"So that kind of wraps up his career certainly with Torro Rosso and Red Bull, most probably with Formula One ... maybe it's time for Brendon to start looking at new pastures."

Hartley made his Formula One debut last season at the USA Grand Prix, replacing Gasly for the drive before becoming a fulltime replacement for Kvyat.

He recorded his first Formula One point at the Azerbaijan Grand Prix in April with a 10th placing. Hartley qualified second to last but moved into the top 10 when seven drivers failed to finish the race. The last time a New Zealand driver earned a Formula One point was Chris Amon at the 1976 Spanish Grand Prix.

Hartley followed that up with a 10th at the German Grand Prix in July and a career-best ninth in Austin. He had five retirements from his 21 races this year including a scary crash at the Canadian Grand Prix when he collided with Williams-Mercedes driver Lance Stroll and was pushed into a wall on the opening lap.

It seems unlikely that Hartley will find a drive at another Formula One team next season. All the driving spots are filled except for one with Lance Stroll expected to be announced as the second Force India driver alongside Sergio Perez.