Unrestricted lineman blocking (a little) downfield

[Reffing Rev.]

A snaps from B's 21 yard line and LB B44 steps up in zone/spy coverage standing at B's 18 yardline when unrestricted A60 moves and blocks him at the knees from a 9 o'clock position just as A10 throws a touchdown pass from within the pocket to the left sideline.

Any foul on this play?

I called A60 an inelligible downfield, but am now thinking I should have passed on it.