Russell believed he had a realistic shot at pole position at Yas Marina after topping the final practice session on Saturday afternoon, but he wound up fourth in the evening shootout - lapping 0.343 seconds shy of Red Bull polesitter Max Verstappen.
While Russell reckoned that, in isolation, fourth place was no mean feat, the Briton said the result ended what had been a “strange day” as the grip faded aboard the W14.
He told Sky Sports: “A strange day, to be honest. I think ahead of this weekend, we'd have definitely taken a P4.
“I felt good in the car but after this morning, we seemed really strong and we thought probably pole was possible but we went out for Q1 and we just didn't have the same grip as we had earlier.”
Given the downturn, Russell reckoned he was signing off on “one of the worst seasons of my career”.
Russell, on course to finish eighth in the drivers’ standings with team-mate Lewis Hamilton in third, continued: “I want to finish the season on a high.
“It's been probably one of the worst seasons of my career in terms of results. It's just been just a really scrappy, messy season.
“I don't think it's been through a lack of speed. We've had really strong pace in many, many races but just never achieved that result on a Sunday.”
Russell did not have a complete explanation for the difficult year, instead saying that a confluence of factors underlined a lack of performance that Mercedes could not attribute simply to bad luck.
He continued: “There's a reason every single race [for the issues], whether it's me crashing into a wall [to lose third place on the final lap in Singapore] or the rain coming down in Zandvoort on the wrong lap or the engine breaking down in Melbourne.
“It's just tiny little things which you can say 'Easy to rectify that'.
“But when it happens once or twice, you can put it down to bad luck. When it happens on maybe nine, 10, 11 occasions throughout the year, it's definitely not luck.
“Ultimately, the car isn't quick enough. We need to keep on pushing. When the competition's so high, one small mistake and you drop a number of places.”
