MANKATO — Running back Adrian Peterson caused a stir in March when, just before the lockout, he compared the players' place in the game to "modern-day slavery" during an interview with Yahoo! Sports.

On Friday, he made his first public comment about that remark.

"I regret using those words because obviously there is nothing, absolutely nothing that you can compare to slavery," Peterson said. "It stands alone. It was something that I should have used better wording to put that out there. But it's spoiled milk, it's old and it's over with."

Peterson said coach Leslie Frazier did "not really" talk to him about the situation. "Not in like a sit-down conversation about it," Peterson said. "It was [taken] out of context and it was on me for putting it out there to make it available to be taken out of context."

Longwell perfect Kicking live for the first time in camp, Ryan Longwell had another ho-hum 6-for-6 performance on kicks from 28 to 43 yards. He was 2 of 2 from 43 yards.

Afterward, he talked about the rarity of a team in today's NFL having the same kicker, long-snapper (Cullen Loeffler) and holder (Chris Kluwe) together for six years.

"Obviously, one of the big factors in me coming back and re-signing here was Cullen and Kluwe," Longwell said. " Not only is it rare to have three guys together for six years, but those two guys are also the best at what they do."

Rough day First-round pick Christian Ponder spent Friday working with the second-team offense and learning on the job. He threw two interceptions in 7-on-7 drills, with cornerbacks Devon Torrence and Marcus Sherels getting the picks.

"It's called being a rookie in the National Football League," Frazier said when asked about Ponder's struggles. "There's going to be some other days like that. That's part of it. ... He's going to have a lot of good days, too."

Ponder took responsibility for the interceptions, which were both intended for fellow rookie Stephen Burton. "I think it was definitely good to get that out of the way and learn from it," Ponder said. "We obviously have got a lot of film to watch and those days are where you progress the most from."

Etc. • Anthony Herrera (ACL) remains on the physically-unable-to-perform list and Frazier said he would like to get the right guard into either the third or fourth preseason game so he can play in the Sept. 11 season opener at San Diego.

• Cornerback Cedric Griffin (ACL) might be able to play in the second preseason game at Seattle on Aug. 20. Griffin has been working with the first team at right corner and appears on schedule to definitely be ready to for the Chargers game.

• The Vikings signed defensive tackle Colby Whitlock out of Texas Tech and released wide receiver Ryan Lincoln (Texas A&M-Kingsville). Whitlock, 6-3 and 294 pounds, was initially signed by Denver this summer as an undrafted free agent. Cornerback Marcell Gipson missed the Friday practice because he had a family emergency, according to Frazier.