Ravens Coach John Harbaugh is 49-24 since replacing Brian Billick, and he’s the only coach since the 1970 NFL merger to guide a team to a playoff victory in each of his four seasons. (Nick Wass/Associated Press)

A football coach to the core, John Harbaugh loves motivational quotes and uplifting slogans.

He has some printed on T-shirts and others are framed and strategically placed in his office or around the Baltimore Ravens’ training facility.

One of his favorites, however, still resides in his phone. Seated at a table in his office recently, Harbaugh scrolls down and finds a message from a friend. He then reads the words of Chinese philosopher Lao Tzu. He pauses a couple of times and lets the words sink in. He then reads them again.

“A leader is best when people barely know he exists, when his work is done, his aim fulfilled, they will say: we did it ourselves.”

To the football populace, the Ravens will always be Ray Lewis’s team until the day the indomitable middle linebacker calls it quits on his Hall of Fame career. John Harbaugh? He’s a good coach who has had many great players, they say.

How good?

Harbaugh is 49-24 since replacing Brian Billick, and he’s the only coach since the 1970 NFL merger to guide a team to a playoff victory in each of his four seasons. He’s won with a rookie quarterback and youth at other key positions. His teams have survived injuries, offensive inconsistency and a revolving door of defensive coordinators. They have exceeded modest expectations, and held up reasonably well to enormous ones.

He may not come across as charismatic as Pittsburgh Steelers Coach Mike Tomlin or as quotable as New York Jets Coach Rex Ryan and he receives nowhere near the attention or the credit that his younger brother, Jim, does as the head coach of the San Francisco 49ers. However, Harbaugh’s influence is all over everything the Ravens do.

Under the fifth-year head coach, the Ravens have won consistently with an ever changing roster that now features just six players who were with the organization prior to Harbaugh’s arrival. They’ve done it while playing a physical yet disciplined style, and embracing the concepts and principles that their head coach always preaches.

“In the end, the team belongs to the team,” Harbaugh said. “Yeah, I’m part of that but so is every player and every coach and every person involved. It’s our team. It’s not the coach’s way. It’s the Ravens’ way. It’s how our team operates. It’s having a shared ownership of everything we do. It’s never been my way or the highway here. But the principles, they are rock solid. Like we say to our team, principles are written in stone, methods are not. We will not back down from our principles.”

Starting Monday, when the Ravens host the Cincinnati Bengals and begin another run at that elusive Super Bowl, Harbaugh could face his biggest challenge yet. The Ravens will play eight of their 16 games against teams that made the playoffs last year. They are scheduled to face quarterbacks Tom Brady, Philip Rivers, Tony Romo, Michael Vick, Ben Roethlisberger and both Peyton Manning and Eli Manning.

The Ravens won’t have reigning NFL defensive player of the year Terrell Suggs for most, if not all, of the season, and several key pieces from last year’s 12-4 team, including Pro Bowl guard Ben Grubbs, linebacker Jarret Johnson and defensive coordinator Chuck Pagano, are gone.

“I feel as good about this team as any team we’ve had,” Harbaugh said. “That’s not a predictor about our record or anything like that, but I really, really love this team. . . . Obviously, I feel we’re talented and have a chance to be very good.”