EDEN PRAIRIE, Minn. -- When Derek Cox signed a four-year, $20 million deal with the San Diego Chargers last year, he couldn't have expected to be here, fighting for playing time on a one-year, $780,000 deal with the Minnesota Vikings that offers him little other than an opportunity to reboot his career as part of a fledgling secondary.

Cox played at least 10 games in three of his four seasons with the Jacksonville Jaguars, and had four interceptions in all three of those seasons. It wasn't until he got to San Diego, where he was signed to be a key member of Mike McCoy's secondary, that Cox found himself out of place.

Derek Cox says he was not a good fit for San Diego's defense. AP Photo/Rick Scuteri

The reason for his disappointing 2013 season and abrupt release, Cox believes, was a scheme that didn't fit him well and left him struggling to sort out what he was supposed to be doing. He intercepted just one pass, lost his starting job in November and was out on the free agent market this spring. He saw the Vikings' new defense as a good match, and if he can get back to the way he played for the Jaguars, Cox could be a key contributor to the Vikings' secondary.

"I view it as a prime opportunity," he said. "That's how you have to approach it every day. This is similar to some defenses I've played in before, which helps."

The crux of Cox's problems in San Diego, he said, lay in the Chargers' practice of having their cornerbacks travel across the field with receivers, which allowed teams to line up a receiver outside, motion him inside and essentially turn Cox into a slot cornerback. That wasn't a role he was comfortable playing, and as Vikings fans saw with Josh Robinson last year, the slot cornerback position can be a harsh adjustment for a cornerback used to playing outside and being able to use the sideline as a second defender.

"Cornerbacks could travel across the ball, running with motion, and you'd be in a zone coverage," Cox said. "Turned you into a nickel back, you'd be in a base [defense] and run to other side in zone coverage, you'd turn into the nickel."

In Zimmer's defense, cornerbacks are rarely asked to travel across the field, instead staying on one side of the formation. Things will be simplified, and Cox will get to play plenty of press coverage, which is what he does best.

He intercepted Christian Ponder on a ball over the middle during the Vikings' organized team activity on Thursday, and coach Mike Zimmer said Cox has been showing steady improvement.

"He is a smart guy. He's got good size," Zimmer said. "He's catching on to the defense we're trying to teach, and really, he's been getting better every single day that we've had him."

Cox's work has been coming with Robinson sitting out because of a nagging injury, and it's possible Cox could be an outside corner in the Vikings' nickel package, with Captain Munnerlyn sliding inside. That kind of a role, he hopes, could put him on track to being what he was before last season.

"It's pretty much left, right; man, zone principles. I play a ton of press coverage," he said. "With my size (6-foot-1), my arm length, it's an advantage. [The defense] plays to my skill set."