ST. LOUIS -- While the Cardinals' winter work is all but certain to include the acquisition of at least one late-inning reliever, the organization will also have some critical decisions to make regarding the fits of those returning.
Among the more intriguing cases is Sam Tuivailala. After years of yo-yoing between Triple-A and the Majors, he will enter 2018 out of Minor League options. That means that if the Cardinals do not include Tuivailala on their 25-man roster, he would be placed on waivers and available for another team to claim.
That's an unlikely path for the Cardinals to pick, as Tuivailala has given them reason to consider him as a viable option for the Opening Day bullpen. A converted position player, Tuivailala showcased improved command of his fastball and a renewed confidence in his curveball last season. His usage of the curveball jumped from 9.5 percent in 2016 to 19.3 percent in '17.
"I think he's shown a deeper set of weapons, maybe, than what he showed a year ago," manager Mike Matheny said. "He's continued to kind of move his way up in how we view him. He's put a little movement on the fastball. The breaking ball is a little more consistent. And he's got the good life with the strong arm. He's taken the proper steps at the proper time."

The Cardinals tested Tuivailala by inserting him into higher-leverage situations down the stretch in September, and he responded with a flourish of a finish. Over his final eight appearances, Tuivailala scattered five hits, allowed one run, walked none and struck out six.
In 37 appearances with St. Louis last year, he posted a 2.55 ERA. He complemented that with a 1.27 ERA over 18 Triple-A appearances.
"I think I showed that I have confidence in throwing all of my pitches for strikes," Tuivailala said of his development. "I'm really happy about how I attacked hitters this year, and that I limited walks. That's a big thing that I really wanted to cut down this year. You can't give up free bases in this game."
After allowing an average of 5.8 walks per nine innings from 2014-16, Tuivailala lowered that to 2.3 last year. He didn't issue a walk in his final 13 appearances.
"I feel like I competed really good this year," said Tuivailala, who turned 25 last month. "I definitely think it was difficult at first, going back down and coming back up. That can be hard sometimes from a mental standpoint. But this year, I'm really happy with how it went. I think everything is coming together pretty good."
The Cardinals are likely to open next season with two out-of-options relievers, as Tyler Lyons falls in that category as well. How the club fills its other bullpen vacancies will depend on its level of winter activity. Matt Bowman, Brett Cecil and John Brebbia will likely factor into the mix. So, too, could some of the team's ascending starters who don't have an immediate fit in the rotation.