Depends on whom they get to replace them.
But the Lions have strong lines which make any coordinates look better than they actually are, so possibly they won't be hurt as much as some think.
But Ben Johnson was very creative, and I thought used QB Jared Goff extremely wisely and basically made him a game manager and let the other guys be the play maker.
If you don't get an offensive play caller that sets up Goff right, I could see that knocking them down a peg.
That being said, Ben Johnson is still in the division, and now he's with the Bears, which clearly have a much worse OL, but might have a better QB.