Quarterbacks Logan Thomas (6) and Phillip Sims (1) get work during a recent practice.

The competition between Logan Thomas and Phillip Sims seems close. Now it may get heated.

The battle for the Cardinals' third quarterback job is an intriguing storyline, especially after the injury woes suffered at the position in 2014. Following the release of Chandler Harnish, it now exclusively features Thomas, the raw former fourth-round pick with tools, against Sims, the highly-ranked high school star who never found his footing in college and went undrafted.

After watching the duo compete for a few months, coach Bruce Arians is muted with any excitement.

"They're like a roller coaster ride," Arians said. "Good one minute – not one day, one minute – and then bad the next. They need some level of consistency throughout camp, and they have limited reps. It's hard to blow (those reps) when you get them."

Preparing quarterback Carson Palmer for the regular season is the top priority during practices, while Drew Stanton gets his share of

work. Preseason games, though, allow the backups to get meaningful action.

The Cardinals begin their preseason slate at home on Saturday against the Chiefs, where Thomas is expected to play the second and third quarters and Sims the fourth. While neither has stood out at training camp, Arians puts heavy emphasis on game performance.

"Some guys, when the lights come on, they're special," Arians said. "Other guys shudder. That's what you're always looking for when those lights come on. How do they handle it?"

It's unrealistic to think Thomas or Sims can flip a switch and become an above-average quarterback this preseason. Some players might turn it on more in games, but as Palmer and safety Tyrann Mathieu have proven throughout training camp, the top players distinguish themselves no matter the situation.

For now, Thomas still must curb his inaccuracy. On some throws, his potential is laid out in clear sight, as he fires a fast, crisp ball to a receiver. On others, a simple throw to the flat gets airmailed.

"Lazy footwork," Arians said.

Sims has a more consistent touch on his throws, but is smaller and has less arm strength. While neither has been consistent, there's still the feeling Thomas has the upper hand because of his draft status and higher athletic ceiling.

That seems to be the way both quarterbacks are approaching it.

"I feel like it's my job to lose," said Thomas, though he knows he hasn't clinched it. "Just going out there and doing what I have been doing isn't going to make sure I'm the Number Three. I've got to go and press to be the best I can be every day."

Sims doesn't seem rattled by his underdog status. He said his first NFL game isn't a landmark achievement but the next step in the competition – a ride which he has simplified despite the enormous stakes.

"Like I tell people all the time, nobody thought I'd be here in the first place," said Sims, who was signed after a tryout. "There ain't no pressure on me."

There is another option for the third quarterback spot: No one at all.

Despite last year's injury problems, it's more likely than not a third quarterback never sees the field in 2015. If Sims and Thomas fail to impress, Arians could use the roster spot at a different position and possibly stash a quarterback on the practice squad.

It hasn't been the smoothest of starts for Sims and Thomas, but both hope to show they deserve to be the third quarterback, beginning Saturday against the Chiefs.

"You're only going to get, being a third guy, so many opportunities," Palmer said. "You're so focused, and you don't want to focus on mechanics and you don't want to think about accuracy, you want to be able to go out and play free and fast. But with limited opportunities and limited reps you just don't get that chance to really hone in on certain things and go back and watch the film at night, really pick on one or two things to work on. When you're the third guy, you don't have that luxury.

"You're trying to shine, you're trying to move up the depth chart, you're trying to prove yourself, you're trying to knock out all those accuracy concerns that you've been hearing about for years. It's difficult, but this game is difficult."