I think it's six, and I think this is a pretty good idea, since Torkleson and Greene might be free agents in 6 years. Rodriguez's 5 years lines up neatly with Mize/Skubal, if the next CBA is similar in length to previous cba.
The Lions run a 3-4, so they needed different defensive linemen to begin with. They needed a nose tackle, and got the only one in the draft. That's a lot of position value on the 2nd day.
Just a reminder that the tank is going well, they should have the #1 pick sewed up soon. They have room for error, so they can win a game, preferably against Chicago, but that's not entirely necessary.