Michael Crabtree played for Jim Harbaugh for four seasons.
At the conclusion of the 2014 season, Harbaugh left the 49ers for Michigan, and Crabtree left the 49ers for the Raiders.
On Wednesday evening, the wide receiver talked about his former head coach.
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SIGN UP HERE "Harbaugh is something else, man," Crabtree told KNBR 680 AM. "That's one of my favorite dudes, man."
Harbaugh has made headlines recently for his unusual recruiting tactics.
His methods paid off on Wednesday, when Harbaugh secured the No. 6 class in the nation, according to numerous recruiting outlets.
"He just likes to compete," Crabtree explained. "It's just being competitive. Everything we did at practice, from little drills, we used to always compete ... just a good, tough competitor. That's really his personality."
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[REWIND: Crabtree: 49ers made offer, needed QB 'that can deliver the ball']
Did Harbaugh's antics ever wear Crabtree out?
" No," Crabtree answered. "We the same. We got a lot of energy. Athletes. We competing every day -- playing pool in the locker room, shooting into the trash can -- it's competitive, man."
Crabtree tied career highs in catches (85) and touchdowns (9) in his first season with the Raiders, and signed a four-extension with the Silver and Black in December.
He built a strong rapport with Derek Carr and is excited about the future of the franchise.
"Sometimes you just hit it off," Crabtree said. "With Carr, we hit the field running. He threw the ball in the air and I caught it, and after that, we just got that trust. It's something that just happens."