Russell added to BBC Sport: "Toto has made it clear to me that how I'm performing is as good as anybody.
"There is only one driver that you can debate in terms of performance. These are his words and not my words, and that is why I have no concern about my future.
"But there are two seats to every team and I guess he needs to think who are those two drivers."
Russell's comments imply that his own contract talks with team principal Toto Wolff are being delayed by Mercedes' conversations with the four-time champion.
Wolff said at the Austrian Grand Prix on Friday: "George has always performed to the expectations we set. We haven't given him a car to win the world championship in the last three years and that's on us.
"The times the car is good, he has been winning races. You know he is going to extract what's in the car.
"In a normal business the contract discussions are not being held as town halls, everything is normal, everything is going to plan."
In direct response to Russell's comments on Verstappen, Wolff said: "You are going into territory I don't want to discuss out there. People discuss and explore, and in our organisation people are transparent. But it doesn't change a millimetre of my opinion of George."
Verstappen refused to directly comment when he was asked on Thursday whether he would be staying with Red Bull next year.
"I don't think we need to talk about that," he said. "It's not really on my mind. Just driving well, trying to push the performance, and then we focus on next year."