Mike Krack did not want to make the same "easy excuse" Fernando Alonso gave when assessing his team's decline in form in recent weeks.
Aston Martin lie third in the constructors' standings while Alonso is in the same position in the drivers' table. But those facts mask the team's downward trend in their most recent outings.
The Spaniard finished fifth in Austria and followed that up with seventh at Silverstone. Last weekend, team-mate Lance Stroll joined him in the top 10 in Hungary, but they were in the last two points-paying places and took home just three between them.
It means they are falling well behind Mercedes in the race to be best of the rest behind Red Bull this season. And Ferrari have closed the gap behind them, despite the Italians' own problems.
Speaking in Budapest last week, Alonso blamed a change to the Pirelli tyres being used for the decline of his team's competitiveness. "It is [not] a coincidence that when the new Pirelli tyres came in Silverstone there are a couple of teams that were struggling more, and a couple of teams that are very happy with the car now," he said.
Sebastian Vettel warns of looming F1 ban and is "very worried about the future""It's not only us, I think Red Bull has clearly been hit with those tyres. They've been one-two in every qualifying, one-two in every race, and now they are not even on pole position. Checo [Perez] is struggling to be in the top 10. At Silverstone I think Max was only three seconds in front of Lando [Norris]. So I see things a little bit abnormal since Silverstone."
But team principal Krack does not agree with his driver. Posed those comments by reporters on Thursday ahead of this weekend's Belgian Grand Prix, the Luxembourger said blaming their struggles on that one reason "would be an easy excuse".
He said: "We see there is a little difference with these tyres but they were brought for safety and so from that point of view, everybody has to run them and are the same for everybody.
"We should not use this as an excuse for competitiveness because they are the same tyres we have to use going forward. It's about learning as much as possible about them and moving on. It would be too easy to say it is the tyres.
"At the time Fernando was saying that, the situation was different in terms of competitiveness. In the meantime, other teams have caught up and brought performance to their cars, which we didn't manage. That is the main why we fell back and why we were slower than we were hoping we were."