Red Bull unsure of cause of Verstappen's cracked rear wing

After Verstappen had produced a strong lap in final practice before it was deleted for track limits, Red Bull discovered there was a visible crack in his rear wing.

The team elected to make repairs to it to beef it up before qualifying, as well as strengthening the wing on teammate Sergio Perez’s car as a further precaution.

But without a definite answer as to what caused the problem, Red Bull will conduct further investigations overnight before deciding if the wing will be OK for the race.

“There's always something going on,” Horner told Sky Sports F1. “There's never a stress-free session.

“I don't know whether Max hit something, as [there was] quite a crack, and nothing on the other car or any of the other wings.

“We got permission just to beef it up a bit on both cars, so we'll have a closer look at it tonight.”

Sergio Perez, Red Bull Racing RB16B, in the pits during practice

Photo by: Mark Sutton / Motorsport Images

Despite the concerns about the rear wing, both Verstappen and Perez were able to produce strong qualifying sessions as they kept title rival Lewis Hamilton at bay.

And with Mercedes having not been able to build on the pace-setting form it showed in opening practice, Horner says Red Bull had managed to make good gains.

“Yesterday the set-up we arrived at the track with was a little bit out, but I think we just tuned the car in,” he explained. “We've managed to improve the traction and we've managed to improve the car a bit over the bumps. The drivers are definitely... you can see their confidence has just grown and grown. So that was a big factor.

“And I think particularly on the mediums, we were debating at one point, would the medium be the better tyre for Q3?”

Mercedes reckoned that the story of the weekend so far was that Red Bull had indeed made good progress with its speed, while the world champion outfit had pretty much stood still.

Chief technical officer James Allison said: “After FP1, FP2 was a bit more of a struggle and it's been a little bit that way since. We've been up at the sharp end, but not really with the edge that we've seen in the recent races, so not easy.”

Asked if it was more Mercedes had lost speed or Red Bull had gained, Allison said: “Probably a little bit of each. Remember we are running in qualifying very similar set-ups to where we started in FP1, having migrated a bit in between time and then come back. So I think probably it's a bit more of Red Bull having a stronger weekend of development than we did.”