Kansas City, Mo. ? The biggest reason that Chiefs quarterback Alex Smith pressed his representatives to get a long-term contract done before the start of the regular season was simple peace of mind.

“It’s all on football now,” he said. “It’s not sitting in the back of your head — ‘I’m playing for a new contract’ — as you go out on the field, week after week.”

Jake Locker is about to learn all about that situation.

The Titans declined their fifth-year option on the injury-prone Locker in the offseason, making this a critical year for him. He’s shown plenty of promise his first three seasons, and was poised to have a breakout 2013 before another round of injuries prematurely ended his season.

Now, when Locker leads Tennessee into Kansas City in the season opener for both teams today, he’ll be trying to show Titans brass that he’s their long-term answer — which happens to be exactly what the Chiefs are gambling they have in Smith.

“You never know which game throughout the course of the year is going to be the one that changes your opportunity to go to the playoffs or not, so you got to treat each one like that,” Locker said. “Each one’s a must-win, because you don’t know what you’ll look back on and go, ‘Gosh, if we just would’ve found a way to win that game we would’ve found our way into the playoffs.”

Or, if they just would have made the playoffs, Locker would have his new deal.

Smith earned his four-year, $68 million extension from the Chiefs last weekend largely because he was able to guide them to the postseason. He took over a two-win team and went 11-5 in his first year in Kansas City, playing well in a 45-44 loss in Indianapolis.

The Chiefs will be trying to build on that turnaround in not only their second season with Smith, but also their second season under Andy Reid.

“Big Red” immediately brought stability to the franchise when he arrived last offseason, and that feeling has carried into this season.

“The big thing now is just to finish,” Chiefs safety Eric Berry said. “Whether it’s winning, a play, a drive, a game, whatever, it’s just all about finishing.”

It’s about finishing in Tennessee, too, after the Titans blew a fourth-quarter lead against Kansas City a year ago. But it’s also about starting: The Titans are in their first year under Ken Whisenhunt, who spent last season as offensive coordinator in San Diego.

“The stuff that we’re doing right now, this practice, that’s not the fun part. The fun part is on the field on Sunday,” Whisenhunt said, “and seeing what you’ve worked so hard on and realizing some of those results. It’s a struggle every week, and hopefully we’ll be prepared.”

Here are some things to look for when the teams take the field:

Key suspensions: The Chiefs will be without top pass catcher Dwayne Bowe, suspended for the opener following an arrest last November, and right tackle Donald Stephenson, who will miss the first four games for violating the NFL’s performance-enhancing drugs policy.

Offensive line: The only offensive lineman who started in the same position for the Chiefs last season was center Rodney Hudson. Left tackle Eric Fisher has moved over from the right side, left guard Jeff Allen will be starting in Stephenson’s place at right tackle, recently signed Mike McGlynn has taken over at left guard and sixth-round pick Zach Fulton is at right guard.

Defensive titans: The Titans switched to a 3-4 scheme under new coordinator Ray Horton, giving up an opening touchdown drive in all four preseason games. Defensive lineman Jurrell Casey, who just signed a $36 million extension, may have said it best: “No touchdowns on the opening drive. Very important. It’s something that we struggled with in the preseason, and it’s something we can’t allow to transfer into the regular season.”

Running backs rule: The Chiefs’ Jamaal Charles is coming off a big season, while the Titans will be leaning on a running back-by-committee approach. Chris Johnson is gone, so veteran Shonn Greene, rookie Bishop Sankey and former Chiefs standout Dexter McCluster will share the load.

On road again: The Titans opened the 2013 season by winning in Pittsburgh, and now they’re back on the road. “It’s not always that much fun to open on the road,” said left tackle Michael Roos, going into his 10th season. “Last year we opened at Pittsburgh, which is a great place, and obviously Arrowhead is one of those meccas of football. And as soon as the crowd yells ‘Chiefs!’ at the end of the national anthem, you’ll get those goose bumps again and it’ll be go-time.”