If Jamaal Charles, Jeremy Maclin, Travis Kelce and De'Anthony Thomas are a few of the amenities, then the engine behind the Kansas City Chiefs offense is the offensive line.

Just like a car, if things aren't right with the engine, then the playmakers can't do their jobs.

For the Kansas City Chiefs in 2015, there are only two players who return along the offensive line that played significant snaps for them last year.

Allen is coming back from an injury suffered in Week 1 of last season. Throughout OTAs and minicamp, he's spent time rotating between right guard and right tackle.

The Chiefs traded with the New Orleans Saints for two-time Pro Bowler Ben Grubbs earlier this offseason. They also signed veteran Paul Fanaika and spent their second-round pick on former Missouri Tiger Mitch Morse.

Bringing in new faces to compete for the five starting spots on the offensive line was obviously important to general manager John Dorsey and company.

They had a plan and they stuck to that plan.

It's safe to believe Fisher and Grubbs will handle the left side of the offensive line, but the other three spots will be figured out between the start of training camp and the first regular season game in Houston on September 13.

Joining Fulton, Allen, Stephenson, Fanaika and Morse in competition for these spots will be second-year player Larry Duvernay-Tardif, third-year center Eric Kush, who took many of the first-team reps at center during OTAs and minicamp, and Derek Sherrod, the former first-round pick of the Green Bay Packers in 2011, among others.

Here are three storylines to watch along the offensive line during training camp beginning on August 1:

Eric Fisher's first full healthy offseason

There's always going to be a certain kind of microscope on Fisher, and that comes with the territory of being a former No. 1 overall pick. The good news for Fisher is that he's coming off the first healthy offseason of his career. He had shoulder surgery last offseason and wasn't able to do much of what was needed to be anything but healthy by the time the season came around.

But this year, Fisher said he did quite a bit of boxing over the offseason and has never been in better shape. The ability to lift weights with his upper body will obviously only help him as he gets ready for his third season as a pro.

Fisher will look to pick up where he left off last season, when after giving up seven quarterback hits in the first two games, he surrendered just four total throughout the final 14 games.

What happens at center?

Throughout OTAs and minicamp, third-year player Eric Kush took the majority of the first-team reps at center.

Kush has been in this system for the past two seasons after being the Chiefs sixth-round pick out of California (PA) back in 2013, so there's a certain familiarity with the offense.

In his two seasons, Kush has played 73 snaps, almost all of which came against the San Diego Chargers in Week 17 of the 2013 season.

Morse, who also took some time with the first-team offense at center, has the kind of talent that warrants watching him throughout training camp. The coaches have already praised his athleticism and versatility throughout the offseason.  

He's talented and was a priority draft pick by the Chiefs, being taken in the second round. He also spent some time at right guard this offseason.

What happens on the right side of the offensive line?

Last year, Zach Fulton stepped into the starting lineup as a rookie at right guard. Throughout OTAs and minicamp, Allen, Morse and Tardif had been just some of the names mixing it up at that right guard spot.

At right tackle, Stephenson and Allen have split the majority of the snaps, but coach Andy Reid has consistently said they'll find the best five players to start along the offensive line.

While the left side is pretty solid heading into the regular season, the right side of the offensive line will be something to watch as we head into training camp.

There's nothing more important to the success of the Chiefs offense in 2015 than the strength of the play up front, and the five players who will be holding down those spots is not yet known, which is why it's the top storyline of training camp.