Assuming the worst would leave Tampa Bay without Tanard Jackson and Aqib Talib. Many ideas are being thrown around as far as getting a free agent cornerback like Antonio Cromartie, Nnamdi Asomugha, and Jonathan Joseph. Concerning safeties- there hasn't been nearly as much speculation.
The free agent safety crop is by no means stellar this off season, but the name that jumps out is Eric Weddle. San Diego placed a first round tender on him in March, however established tenders may not be binding depending on the outcome of the new collective bargaining agreement. Should the new agreement render the tenders void, Weddle will be courted by several clubs.
I like Weddle for Tampa because of his intelligence. He's quick, has adequate ball skills, and is a sure tackler. Weddle performs well in coverage and against the run- this set of skills would upgrade the position for the Bucs substantially. He's only 26 years old and hasn't any character concerns. Given his awareness on the field and the schematic positional similarities, I believe he could play either FS or SS in Tampa's defense.
Mostly I cannot stress the importance of his tackling ability. Cody Grimm performed well in that regard while Sean Jones was merely satisfactory. Having a safety on the roster who breaks down and wraps up saves a lot of points. Weddle could help guide Grimm with his covering techniques and turn him into a serviceable starter who could be reasonably better than Jones.