Marko's comments come on the heels of Red Bull team principal Christian Horner’s remarks about evaluating future driver options, including Russell, whose Mercedes contract ends in 2025.
"George is on par with Hamilton in qualifying, if not even faster," Marko said to Formel1.de.
While Russell finds himself 19 points behind his Silver Arrows team-mate in the drivers' championship, the 26-year-old has bested Hamilton 13-5 in qualifying so far over the season.
Despite backing the Brit, Marko admitted the aim for Red Bull is to focus on drivers within their own pool, going against Christian Horner's comments.
The Austrian said: "But George Russell is somewhat branded by Mercedes. Now, I believe we should focus on our juniors."
Red Bull's discussion around the 26-year-old's future all stems from their team principal Horner, who hinted Red Bull would not rule out the possibility of considering drivers outside of their in-house talent for future seats.
He pointed to drivers like Yuki Tsunoda as examples of the talent pipeline Red Bull is investing in, rather than looking externally, despite admitting young talent like Franco Colapinto presents an exciting opportunity.
"Take Colapinto, for instance; he’s relatively inexperienced and hasn’t had much success in the junior series," Marko said.
"I must say he’s never had the optimal teams, but the incredible performance he’s delivering now is impressive.
"We want to see what our juniors can do, and you could consider Yuki Tsunoda a junior as well. But how does he compare to someone like Lawson, for example?"
With the highly-rated Kimi Antonelli replacing the Ferrari-bound Lewis Hamilton for the 2025 season, Russell is set to become the main man at Toto Wolff's team.
Whilst Marko may have been impressed by Russell, it remains highly unlikely that the Briton would be willing to jump ship just to play second fiddle to yet another multiple-time F1 world champion.