Verstappen took pole at Suzuka by roughly six tenths ahead of McLaren duo Oscar Piastri and Lando Norris.
Having both drivers in the top three was a huge result for McLaren, but at the same time Stella felt it was humbling to see how much faster Verstappen was on the challenging layout, having hoped that his drivers would be closer to the Red Bulls.
"We expected to be more competitive than Singapore," Stella said. "We were unsure as to whether this would have put us as second best team, or whether Mercedes and Ferrari would have been there with us.
"We were pretty certain that Red Bull would have been the quickest car here, considering the track layout.
"If you look at the overlays, Verstappen gains in every kind of speed range, so it's quite remarkable. It gives us again the measure about how much work we have ahead of us."
Source: Autosport