Emphasizing surprise and versatility, Buffalo Bills first-year defensive coordinator Mike Pettine is unveiling a new scheme designed to keep opponents guessing.

If that leads to some Bills initially experiencing difficulty identifying what position they're playing, Pettine's fine with that, too.

"'I don't know,'" he says, smiling, "is a good answer."

Pettine is responding to comments made by several Buffalo veterans in sharing their first impressions of a defense geared toward creating mismatches by having players learn multiple roles. Three weeks into spring minicamps, the question becomes how quickly the Bills can adapt to yet another new system — their third in three years.

Pettine's part of coach Doug Marrone's new staff after spending the past four years holding the same job with the New York Jets.