Russell raced for Mercedes at the Sakhir Grand Prix after seven-time world champion Lewis Hamilton tested positive for COVID-19, and came close to scoring his maiden F1 victory before eventually finishing ninth.
As Mercedes waited to learn whether Hamilton could race in Abu Dhabi, Russell took part in Thursday’s media duties for the team, only for it to be confirmed later in the day that he would be returning to Williams for the rest of the weekend.
Russell conceded that he had mixed feelings upon hearing he would be going back to Williams for the race, having wanted to put together a full weekend for Mercedes with greater preparation.
“It was a strange feeling, to be honest,” Russell said.
“Prior to Bahrain, I really wanted to have the two weeks in the car, purely because I was expecting to learn everything I needed to in Bahrain and I could have come here with no excuses, as such.
“As Bahrain did go so well from a performance perspective, part of me was like you know what, I think it was a good weekend, obviously I really wanted to win and I would have had a great opportunity this weekend.
“But nevertheless, these guys at Williams, they gave me that opportunity, they’ve been working so hard for me over the last two years.
“It’s my duty to send off the season on a high, and that’s what I’m here to do.”
Russell got back into the Williams FW43 car for practice on Friday at the Yas Marina Circuit, and ended the day 2.5 seconds slower than pace-setter Valtteri Bottas in the Mercedes.
The 22-year-old said it was “very different” driving the Williams once again due to the shift in pace.
“There’s no hiding the laptimes, obviously that’s clear,” Russell said.
“Mercedes is the benchmark. I was fortunate enough to race for them last week and know where we need to be pushing the car.
“It’s good learning, and to get that back-to-back in the space of five days was great.”
Russell was able to score his first F1 points in Sakhir with Mercedes, but was unsure of repeating the feat with Williams in the season finale barring setbacks for the cars further up the order.
“We’ll be trying our everything,” Russell said. “I think it gets to the last race of the season, I think everybody up and down the grid gets a bit desperate.
“There are a few teams fighting over that P3 spot, so we might see some big lunges. Carlos [Sainz Jr.] is off to Ferrari, so he probably won’t care if he bashes up the car, then you’ve got Danny Ric [Ricciardo] is off, so he probably doesn’t care if he bashes up the car.
“Who else is going? Sergio [Perez]’s off, so he won’t care if he bashes up the car. It could be a good one.
“But on pure pace, we know we won’t be fighting for the top 10, in all honesty. Kimi [Raikkonen] looked really fast, and Kevin [Magnussen], but that’s usually the case.
“We’re usually a bit off on Friday, and we usually sort it out on Saturday.”