I'm assuming we won't be able to spend much on a tackle, so if necessary, keep 4 of the 5 starting O Linemen and add a Center. I also would be surprised to see Mack get out of Cleveland, but you never know. (especially with that front office).
Michael Bennett would be good. or Michael Johnson, or both.
And another we should sign, who for some reason is unwanted by Bears fans: Henry Melton. He made the pro bowl in 2012 and played great. He went out in 2013, and our D fell off like nothing we've ever seen. Why not "add" a guy who could help turn that back around to the good?
Last year I wanted 5 new O linemen. We got 4, and a total turnaround.
This year, we all want a whole new D line. I don't know what $ Melton will command, but with him coming off injury, we may get him to sign at a good value. Then keep Ratliff and add the DE's mentioned above.
Not sure what LB's are available. We could certainly use a MLB, to put it mildly. Is Orakpo worth a look?