Associated Press

CHARLOTTE — When a four-story condominium building across the street from the Carolina Panthers' practice fields went up several years ago, the running joke had the team's divisional opponents pooling their money to buy a unit on the top floor.

When the building caught fire a few years later, the joke was the Panthers had something to do with it.

Today, the condos are still there, but the view has changed. Strategically planted trees and a tarp over the black iron fence surrounding the fields make it difficult to see anything from a condo balcony.

Welcome to the paranoid world of the NFL — brought to light this week by the New England Patriots' spying scandal.

"I think there's an advantage if you know what's going to happen before it happens," Panthers coach John Fox said. "You always worry about that, whether it's the playbook or signals. It's just like in baseball, they try to protect their signals. But sometimes people get them."

The NFL is investigating whether a Patriots video assistant was taping the Jets' defensive coaches last Sunday as they signaled to players on the field during New England's 38-14 victory.

"If you were doing hand signals and they had it down and they were able to give it to a quarterback, that could be a long day," Panthers defensive end Mike Rucker said. "It could be a long day for you."

Hence, the secrecy. And for the Panthers, it's more difficult to keep people away. Their open-air practice fields, next to Bank of America Stadium, are on the outer edge of downtown and visible from nearby skyscrapers.

For some time, Fox has talked about building a bubble over the practice fields — not for the few rainy days, but to keep people from peering in. The Panthers already employ a security team that watches practice and chases away anyone who stops along the fence and might stumble upon inside information.