Chip Kelly and his offense have found their first lieutenant.

The new San Francisco 49ers head coach hired Curtis Modkins to be his offensive coordinator. Although Kelly will call plays for the 49ers, Modkins will be heavily involved in game planning and the ground attack, where the vast majority of his experience lies.

Modkins comes to the Bay Area via Detroit, where he served as the Lions running backs coach for the last three seasons.

Here are five things to know about San Francisco's next offensive coordinator, a position previously held by names like Mike Holmgren, Mike Shanahan, Marc Trestman, Mike McCarthy and Norv Turner.

1. He has coaching experience on both sides of the ball

After finishing his playing days at TCU in 1992, Modkins got his start as a graduate assistant for the Horned Frogs in 1995.

Despite ranking eighth on TCU's all-time rushing list, which is topped by future Hall of Famer LaDanian Tomlinson, Modkins coached defense for much of the early portion of his career.

He led TCU's secondary for a season, New Mexico's cornerbacks for four seasons and Georgia Tech's defensive backs for another.

"Sometimes we get kind of pigeonholed as coaches because we only see things one way," Modkins told buffalobills.com in 2010. "Being on defense helped open my eyes and see the game from a different perspective. Having an understanding of how defensive players think and what they're taught to do, that has helped me open my vision up."

2. He is a three-time alum of the Bill Walsh NFL Minority Coaching Fellowship program

Modkins spent training camp as an intern with the Philadelphia Eagles in 1997, Dallas Cowboys in 1999 and Pittsburgh Steelers in 2005.

His time working in Dallas under then-head coach Chan Gailey proved to be the most impactful on his career path. After Gailey left the Cowboys, he took the head coach job at Georgia Tech, where he employed Modkins as his defensive backs coach for one season and running backs coach for five more.

Modkins followed Gailey to Kansas City in 2008 in the same role for his first full-time coaching position in the NFL.

3. He's already been a successful offensive coordinator

Following a one-year stint as the Arizona Cardinals running backs coach under Ken Whisenhunt, Modkins reunited with Gailey in Buffalo from 2010-12 as the Bills offensive coordinator.

At that job, Modkins orchestrated a rushing attack that featured the likes of Marshawn Lynch, C.J. Spiller and Fred Jackson.

In 2011, the Bills led AFC with a 4.9-yards per rush average, the team's highest mark since 1975. As a whole, the offense ranked 14th in the league that season. A year later, the Buffalo offense finished fourth in the NFL in rushing average (5.0 yards) and sixth in total rushing (2,217 yards).

"He's a low-key kind of guy, but he will get on you when you're doing something wrong," Jackson said in 2010. "He'll let you know. He'll raise his voice if he has to if you're not getting it done. He's the type of coach you can definitely learn from and respect as a teacher."

4. He comes highly recommended from the Lions

Under Modkins' guidance in 2013, Reggie Bush and Joique Bell became the first running back tandem in NFL history to both register 500-plus rushing yards and 500-plush receiving yards in the same season.

When then-head coach Jim Schwartz was fired after that season, Bush lobbied to Lions management to keep Modkins on staff.

"I definitely wanted to go to bat for him because he's a great coach," Bush told detroitlions.com at the time. "He's singlehandedly helped change the running game of this offense."

In 2015, the Lions finished last in the NFL in rushing, average 83.4 yards per game. But midway through the season, Detroit fired offensive coordinator Joe Lombardi and promoted Modkins to run-game coordinator.

After Modkins took over, the Lions averaged 95.4 yards per game on the ground. Furthermore, Detroit had just one 100-yard rushing game in the first 10 weeks of the season. Then under Modkins' watch, the team had five in its last seven games.

"He played a big role," new Lions offensive coordinator Jim Bob Cooter said. "He's done a good job organizing our run game and sort of getting it headed in the right direction, giving me a lot of input and giving me a lot of wisdom."

5. He's just what Kelly wanted in an offensive coordinator

During his introductory press conference, Kelly gave this quote on ideal qualities for his coaching staff.

"I'm really looking for diversity, someone that comes from another system so that we can continue to add and make what we do better," Kelly said.

Well, that's Modkins in a nutshell.

While Kelly favored zone-blocking schemes with the Philadelphia Eagles, Modkins is more known for his power-run system.

This quote from Modkins on how he approaches teaching players has to be music to Kelly's ears as well.

"My personality is flexible enough that it can adapt," Modkins said. "Whether it's a sterner approach or whether the guy needs more time on the board or if he learns more by walk throughs, I think I've been able to fit how I teach to how they learn."