First, a disclosure about minicamps: Everything the privileged few who watch NFL players run around in June think that they’ve learned can be thrown out when training camps start in six weeks.

That’s when pads go on, and jobs are won and lost. But the NFL is a 24-7-365 league in terms of fans’ interest ... so here are some takeaways from the Raiders’ three-day minicamp that concluded Thursday:

•Derek Carr appears to be fine. He didn’t throw for a month this offseason with a mysterious hand injury, but the second-year-quarterback was zipping the ball pretty well this week.

“Each day he has gotten better, but there is some rust,” offensive coordinator Bill Musgrave said. “He still has that ability, and he was able to get back on the bike and feel natural and normal. The timing and the rapport with the receivers, that will come with time.”

•The Raiders might have their best receiving corps in a long, long time. First-round pick Amari Cooper, besides the occasional drop, looks as good as advertised. Former 49ers wideout Michel Crabtree has showed off his good hands, and Rod Streater is abusing cornerbacks like somebody who hasn’t planned on losing his starting job.

Crabtreeis a happy camper.

“I think he’s done a nice job learning his teammates, learning our system, coming in and working hard,” head coach Jack Del Rio said.

Jeff Chiu/Associated Press

• Pass-rusher Khalil Mack has teammates and coaches geeked at what could be a Pro Bowl season.

“He’s one of a kind in this league,” teammate and former Seattle linebacker Malcolm Smith told SiriusXM NFL Radio. “There wasn’t anybody like him in Seattle. He’s definitely his own beast, and it’s going to be special to play with him.”

Mack, who admittedly doesn’t know how to relax, put on 10-15 pounds of “lean” muscle this offseason and is close to 270 pounds, to deal better with offensive tackles.

When asked where his work ethic comes from, Mack said Thursday, “That comes from getting one scholarship and going to (college at) Buffalo.”

•It’s possible to spend $45 million and still think you got a bargain. The coaches are over the moon about the team’s No. 1 free-agent signee, center Rodney Hudson.

“He’s more than what we anticipated,’’ Musgrave said. “He has better movement than we expected from our film study.”

•Musgrave’s offense will be run-heavy but also mix in some up-tempo, interchangeable-receiver concepts from his last stop in Philadelphia.

“We made some strides, but we have a long way to go,” Musgrave said. “That’s probably the understatement of the year.”

•The Raiders seem genuinely excited about Del Rio, Musgrave and defensive coordinator Ken Norton Jr.

“Oh, it’s a lot of great energy, a lot of positive energy,” Mack said. “It’s a great match having them and us. It’s going to work.”

Vic Tafur is a San Francisco Chronicle staff writer. E-mail: vtafur@sfchronicle.com Twitter: @VicTafur