Nasty play, but I would want to know more. Hard to call this a chop block because it requires a "block" or intentional effort to obstruct an opponent. This was not an attempt to block. Different if this was during a return of some kind. Here, it look like the stand up outside LB was trying to deliver a "pay back" shot to the tackle for some earlier play. So, I would want to know more about what had been happening in the game to guide whether this is a flag or a talking to. Maybe you can make this a personal foul for a hit against a player no longer in the play. But very close to the POA, so hard to make that stick. Not really sure it meets the criteria for any specific foul -- but I do think it is flagrant under 2-10-1 if you can otherwise find something illegal. So, if you throw a foul here, you need to have an ejection. IMO.