Carr and Crabtree later connected for another long gain moments later despite solid coverage from safety Charles Woodson,
Sitting in stands adjacent to the practice field, two-time Super Bowl winning quarterback Jim Plunkett nodded his approval.
The Raiders opened the door to their glorious past and invited more than 50 former players to attend the team's first training camp practice at the request of owner Mark Davis.
Yet all eyes were on Carr and Oakland's current roster of players as they went through a 2 1/2-hour workout on Friday.
''It's just a totally different situation,'' said Carr, who started all 16 games as a rookie last season. ''Just coming in, you know what to expect. You've done it before, you've seen it and you can hit the ground running a lot faster. It's not seeing a new coverage for the first time. You go out and you just play.''
The Raiders hope that having a year of experience under his belt will allow Carr to continue the development that began when he beat out Matt Schaub for the starting job coming out of camp last year.
Oakland beefed up its offensive line to give Carr better protection and signed Crabtree then drafted Amari Cooper to strengthen the receiving corps.
Cooper had a fairly nondescript first practice and caught only a handful of passes during 7-on-7 drills.
Crabtree, who signed a one-year contract with Oakland as a free agent, clearly stood out. He made a long reception after cornerback DJ Hayden deflected the ball, then jumped over Woodson and one other defensive back to catch the second long throw from Carr.
''It's important for any quarterback-receiver relationship to have that chemistry,'' Crabtree said. ''That's what camp is for. I'm ready to attack it more.''
The Raiders' first training camp practice under new coach Jack Del Rio had a different feel from when Oakland opened camp in 2014 with questions about then-coach Dennis Allen's job security.
Del Rio, the former Denver defensive coordinator who also spent nine years as Jacksonville's head coach, watched as his young quarterback completed several passes during a team scrimmage. Del Rio later watched as the defense outplayed the offense during one segment of practice, which ended with the offensive players and coaches doing grass drills together near the middle of the field.
''It was good to get started,'' Del Rio said. ''I think a team comes together in camp, and this is that time of year where we'll need to put in the work and pay the price. We're ready to do that.''
The Raiders had nearly full attendance for their first practice. Backup running back Trent Richardson, wide receiver Rod Streater and linebacker Sio Moore did not suit up because of a variety of maladies. Moore and Richardson worked out with a team trainer while the rest of the team practiced.
In the stands several former Raiders players who are in town as part of the Raiders' alumni weekend took it all in.
The former players didn't just watch the workout. Hall of Fame wide receiver James Lofton gave the team's annual media presentation speech to the younger players Thursday evening, shortly after the players had undergone a conditioning test.
''Once a Raider always a Raider,'' Del Rio said. ''To get a lot of those guys back is awesome.''
Notes: Ray-Ray Armstrong practiced with the first-team defense while Moore sits out with a hip injury. ... Rookie Anthony Morris is backing up veteran Donald Penn at left tackle. ... The Raiders are contemplating using Cooper at punt returner in addition to playing him on offense. The fourth overall pick in the draft, Cooper has not returned punts since high school.
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