For the ketchup: Stir together the ketchup, vinegar, sriracha, Worcestershire and brown sugar in a small bowl.
For the chicken: Preheat the oven to 450 degrees F. Line a rimmed baking pan with parchment paper and spray it generously with cooking spray.
Pulse the pecans in a food processor until finely ground. Add the panko and pulse until just combined. Pour into a wide, shallow bowl.
Put the flour in a wide, shallow bowl and whisk in the garlic powder, paprika, cayenne, 1 tablespoon salt and a pinch of pepper.
Whisk the eggs in another shallow bowl.
Working with one piece of chicken at a time, dredge in the seasoned flour, then shake off the excess. Dip in the egg to coat and let the excess drip off. Add to the pecan panko mixture and turn to coat, lightly pressing so that the crumbs adhere. Transfer to the prepared baking pan.
Spray the chicken generously with cooking spray and bake until golden brown all over and just cooked through, 15 to 20 minutes. Transfer to a platter and sprinkle with the parsley. Serve with the spicy, tangy ketchup on the side.