The Giants ’ defense was humming along in Denver on Oct. 19. Then it collapsed in epic fashion.

A week later, the Eagles gashed the Giants on the ground.

And then, on Sunday, the 49ers had their way with the Giants’ defense, in a 34-24 win during which San Francisco gained 5.8 yards per play and was led by its backup quarterback, Mac Jones.

This latest performance continues a troubling trend for a Giants defense that was supposed to be excellent. And while its secondary was shorthanded Sunday — no Cor’Dale Flott, Paulson Adebo or Jevon Holland — this was yet another underwhelming mess from coordinator Shane Bowen’s group.

When informed of the 49ers’ yards per play Sunday, edge rusher Kayvon Thibodeaux — who almost certainly won’t be traded before Tuesday’s deadline — did not mince

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