ALLEN PARK -- Stephen Tulloch is entering his ninth NFL season, but he doesn't remember a first offseason practice as intense as the Detroit Lions' opening day of voluntary minicamp.

"The energy today was good," Tulloch said. "I've never been a part of a fast-tempo day like this on the first day. Guys were receptive to it and did a good job."

After two weeks of workouts and classroom study, new coach Jim Caldwell was pleased with how his team performed its first day on the field.

"The guys have been working extremely hard the last couple weeks trying to learn the system," Caldwell said. "They came out on the field today and had very few glitches in terms of the things that you normally see on the first day. So that shows me that they do have the ability to concentrate and focus."

Focus is the key to limiting mistakes, a calling card for Caldwell-coached teams.

Caldwell credited the team's veteran leadership for the early success.

"We've got very, very good leadership in terms of the guys that are in the meeting rooms doing a great job of showing the way to some of the other guys," he said. "It's been tremendous thus far."

Caldwell is the sixth head coach Dominic Raiola has experienced in his 13 seasons with the Lions. The difference, according to the veteran center, is Caldwell's quiet confidence.

"It's a calm feeling around the building," Raiola said. "You just get the sense that this guy has been there and done that, and he has. Look at his track record."

That track record includes two Super Bowls rings, one as the quarterback coach and assistant head coach in Indianapolis and a second as the offensive coordinator in Baltimore.

Caldwell's coordinators, Joe Lombardi and Teryl Austin, also bring championship experience as assistants with the Saints and Ravens.

Neither Tulloch or Raiola could offer many specifics about Detroit's schematic changes. Tulloch hinted he'll see more opportunities to blitz this season, while Raiola praised the high-scoring potential of Lombardi's "wide-open offense."

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