Toto Wolff labelled his Red Bull counterpart Christian Horner a "yapping little terrier" as he came to George Russell's defence in his growing feud with Max Verstappen.
A remarkable media day ahead of Sunday's Abu Dhabi Grand Prix started with Russell claiming to ESPN and select other media that Verstappen had threatened last week to "put me on my f---ing head in the wall'."
Russell had been responding to Verstappen's comments about him last Sunday -- the Dutchman had been irate with a grid penalty which cost him pole, one he felt Russell had lobbied for him to get.
In his own media session after the race Qatar, Red Bull boss Horner said: "Yesterday's penalty was more based on hysterics from George, who has been quite hysterical this weekend."
Wolff stepped in to respond to those comments.
In Russell's open media session at the Yas Marina circuit, which Wolff took the unusual step of joining -- he eventually picked up a microphone to defend his driver from the Red Bull pair.
"It's just weak," Wolff said. "At the end, why does he feel entitled to comment about my driver? How does that come? But thinking about it, I've spent 90 seconds to think about it...
"Yapping little terrier. Always something to say."
Wolff added: "I think as a team principal, it's important to be a sparring partner for your drivers.
"And that means explaining that things can be more nuanced. Statements that are absolutistic, taking everything is either right, 100% right or 100% wrong, is something I just think you need to explain, think of more nuance, depending from your perception and your perspective. You need to allow for something to be 51-49, you need to allow for it to be 70-30. There is always another side.
"Maybe when you look at it that way, and you explain it to the drivers and to your team, you come to the conclusion that there is truth on both sides. If you don't do that, you're falling short of your role."
When asked why he had felt the need to attend Russell's session, something he would not normally do, Wolff said Horner's comments had gone over the line.
"I tell you clearly," he said. "There is a thing between drivers, and this is George and Max, and I don't want to get involved in that, but if the other team principal calls George hysterical, this is where he crosses a line for me. Now, his forte for sure is not intellectual psychoanalysis, but that's quite a word. How dare you comment on the state of mind of my driver."
For the avoidance of doubt, Mercedes later clarified that both Wolff's comments had been directed at Horner, not Verstappen.