It seemed like a perfect marriage: Ed Reed would reunite with the Baltimore Ravens to coach a secondary that intercepted the fewest passes in team history.

So why did Reed join the Bills on Wednesday as assistant defensive-backs coach?

It's unknown whether the Ravens pursued Reed for their staff, but he was seen as more of a big brother than a coach during his time in Baltimore. In fact, he was a handful for his coaches throughout his playing days. That part of Reed's career as one of the best safeties in NFL history often goes overlooked.

Ed Reed will reunite with former Ravens defensive coordinator Rob Ryan on Ryan's staff in Buffalo. Tommy Gilligan/USA TODAY Sports

Reed is brash, outspoken and unpredictable. This made him a feared defender (ask Tom Brady and Peyton Manning). It just makes him a question mark as a coach.

How many times did Reed trust his instincts more than the team's game plan? How many times did he continue to lateral the ball after turnovers when coaches urged him not to do so?

Most Ravens coaches and players will acknowledge Reed's brilliance. They will also agree he wasn't the most coachable player. He was a wild card with a mercurial personality.

"Any coach or player that thinks he knows what Ed Reed is thinking or what he’s going to do is mistaken or lying," said Brian Billick, who coached Reed from 2002-07. "He could do things that would make you scratch your head and think, 'What were you doing there?' But it was a whole lot more good than bad. He’s just a different guy that way.”

Current Ravens coach John Harbaugh was recently asked whether he always knew what Reed was doing. "When he told me later, yes," he said.

In hiring Reed, Bills coach Rex Ryan said Reed will be a "phenomenal coach" and will bring a "high level of professionalism." The Ravens sometimes saw a different side of Reed.

In June 2012, Reed became the only player in the Ravens' 20-year history to skip an entire mandatory minicamp without permission. He later tweeted about doing yard work, saying, "Tell the bosses I'm comfortable."

In October 2012, Reed was among the players who reportedly challenged Harbaugh when he announced the team would practice in full pads during its bye. This is why it makes perfect sense that Reed ended up with Ryan, the same coach Reed wanted to succeed Billick in 2008.

Reed is one of the three best players to ever suit up for the Ravens. He is arguably the top defensive playmaker of his generation. He is perhaps the most influential and inspirational figures to ever walk through Baltimore's locker room, even moreso than Ray Lewis.

His incredible body of work earned a place in the Ravens' Ring of Honor and an indelible mark in franchise history. It just doesn't guarantee a spot on the coaching staff.