This is why the Cowboys upgraded the secondary in the offseason: For players such as Vincent Jackson.

The Tampa Bay Buccaneers' receiver visits Cowboys Stadium for the home opener with just nine catches for 175 yards and one touchdown through two games. But in his only appearance against the Cowboys, Dec. 13, 2009, Jackson put on a show as a member of the San Diego Chargers.

He had seven catches for 120 yards. He didn't have any touchdowns, but five of his seven catches were for first downs, and he had two catches of at least 25 yards.

To say Jackson is a big-play threat is an understatement.

Who covers the 6-5, 230 pound receiver? That brings us to why the Cowboys signed Brandon Carr in free agency. Carr is expected to take on the opponent's best receivers, such as Jackson. Carr will press Jackson at the line of scrimmage and try to redirect him from running his routes. Carr has been excellent in man coverage this season but he should expect some safety help, and this is where things could get tricky.

Safety Gerald Sensabaugh is nursing a calf injury and is doubtful for Sunday's game. Danny McCray and Barry Church have three starts combined between them in their careers and most likely will be the starters at safety.

The inexperience at the safety spot could hurt the Cowboys on Sunday when it comes to covering Jackson.

In the first two weeks, defensive coordinator Rob Ryan based his blitzes on how the offenses were running their game plans. If the Bucs try to go deep by targeting Jackson -- he was targeted 11 times with the Chargers back in 2009 -- maybe Ryan dials it up with the blitzes again.

The big problem with covering Jackson is it could open the door for another receiver to go off against Morris Claiborne, Orlando Scandrick and Mike Jenkins. So even if the Cowboys take Jackson out, someone else might hurt them.

Stat you probably need to know: Since 2008, Jackson has averaged 18.1 yards per catch, third best in the NFL.