Red Bull chief advisor Helmut Marko has aired his frustrations regarding the performance of one of his star drivers at last weekend's Hungarian Grand Prix.
The Mexican recovered well on race day to climb through the field and finish two places behind Verstappen in seventh, but his display did little to quieten the doubters given his recent run of poor form.
Perez has scored just 21 points from his previous seven outings, and pressure is building on the experienced racer to show he is deserving of a coveted seat at the reigning constructors' champions.
Writing in his Speedweek column, Red Bull advisor Marko bemoaned Perez's 'typical' performance at the Hungaroring.
The Austrian wrote: "Let's talk about Sergio Perez for a moment: A GP weekend that was typical of Perez, I would say, unpredictable.
"Very good on Friday, only just behind Verstappen and with the best endurance runs of all the drivers, then unfortunately a stupid mistake in qualifying, which resulted in 16th place on the grid, followed by a very strong race up to seventh place.
"He continues to have this up-and-down [season], nobody knows when he will shine or when he will make a mistake - he simply lacks consistently good performance."