The Finn was around 15 kilometres faster than Verstappen in a straight-line, with Lewis Hamilton also using this pace advantage to help his recovery from 11th on the grid to fifth.
Speaking to Austrian broadcaster ORF, Marko explained: "We have to think of something because Mercedes are so fast on the straights.
"They were almost 15 km/h faster here, like when you drive with DRS.
"It's been like this since Silverstone and the gap is only getting bigger."
Since the summer break, Mercedes has outscored Red Bull by 19 points in which time both teams have suffered one non-points finish and one retirement.
Mercedes has also picked up two fastest lap points in this five-race period compared to Red Bull's zero. Both scored five before the shutdown.
"That engine superiority, I don't know what it is and what we can do about it," added Marko. "We need to optimise our chassis even more so that we can balance it out again somewhat."
Team principal Christian Horner confirmed the Red Bull recently asked the FIA to look into the pace, believed to be generated through an intercooler trick, and claimed the team was not alone in raising concerns.
"We raised some questions as all teams do," Horner told Sky Sports F1.
"It wasn't just Red Bull, by the way, there were other manufacturers raising questions as well and continue to be raised.
"It's something I asked the FIA to look at for them to police, but when you've got straight-line speed that's greater than with DRS open, that's pretty impressive."
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