ST. LOUIS -- With a little over a week until Opening Day, uncertainty has mounted in the back of the Cardinals' bullpen, and the question that the team faced in the offseason and spring has become a key intrigue this summer: Who will close?

The Cardinals were not expecting Jordan Hicks, who opted out of the 2020 season on Monday, to be available for Opening Day, and his return timeline was pushing into late September at the earliest because of soreness in his right elbow. John Brebbia, who was positioned to be a setup reliever this year, had Tommy John surgery in June and will miss the entire season.

Giovanny Gallegos, who was going to get a chance to close, has not received clearance to travel from Mexico for undisclosed reasons. Alex Reyes is in St. Louis, but he's not been at Summer Camp, without explanation. Neither has Génesis Cabrera, who the team confirmed tested positive for COVID-19 for a second time over the weekend. Until Gallegos, Cabrera and Reyes can get to Busch Stadium safely, they can’t be part of the closer conversation.

The Cardinals have the depth to fill the bullpen with arms, especially with the young talents they’ve been auditioning in Summer Camp, like Kodi Whitley and Johan Oviedo. The club hasn’t determined roles yet and is stressing flexibility. Cards pitching coach Mike Maddux said that there might not be one answer yet to who will close as the team eases into roles to start the season.

“We have to put our collective heads together and come up with the best recipe for the pitching staff that we can find,” Maddux said. “But I think everybody’s a candidate to do it.”

Here are some of those candidates to watch:

Carlos Martínez

Martínez is still eyeing a spot in the rotation, and the Cardinals would like to give him an opportunity there. After what he showed in spring and is now showing in summer, the Cardinals consider the two-time All-Star starter still part of the rotation conversation. But in a 60-game sprint of a season, St. Louis will need to decide if Martínez is more valuable starting or closing.

Martínez has the recent experience closing, having converted 24 saves in 27 opportunities last season. The Cardinals have Kwang-Hyun Kim for the fifth rotation spot, as well as Austin Gomber and Daniel Ponce de Leon for spot starts and long-relief outings. There aren’t as many like Martínez who profile as a lock-down closer.

“Carlos is an option,” Maddux said. “He’s also an option to start. [He can] throw multiple innings. He’s also an option on the end. … We've got some guys that we know that they’re going to start. Other guys are flexible. Some guys really pitch well, and they deserve a spot, whether that’s going to be [multiple innings] out of the 'pen or starting the game. Everybody’s going to be important.”

Andrew Miller

Miller has well-chronicled experience closing, but the Cardinals might want to see him bounce back from a career-high 4.45 ERA as a reliever last season, when the lefty converted six of 11 save opportunities. Miller has looked strong in camp so far, which is a good sign after he was working through a lack-of-feel issue during Spring Training. Miller converted 36 of 38 saves and compiled a 2.04 ERA with the Yankees in 2015. In ’16, he had a 1.45 ERA and converted 12 of 14 save opportunities with the Yanks and Indians, then served as Cleveland's linchpin in their march to the American League pennant. If Miller can return to even close to that form, he’d be a sure fit for the ninth.

Ryan Helsley

Helsley showed off his fiery, 100 mph fastball as a rookie last year and did well in the opportunities he was given, posting a 2.95 ERA in 36 2/3 innings across 24 games. He offers some versatility as a long-inning and high-leverage reliever, but the Cardinals have had Helsley pitch in one-inning bursts during Summer Camp, hinting how they’ll use him. He doesn’t have the closing experience and blew his one save opportunity last season. But his postseason experience shouldn’t be ignored -- the right-hander didn’t allow a run and he gave up just one hit in 5 1/3 innings in the National League Division Series and NL Championship Series.

“It was huge to go in there and throw up some zeroes and put the team in a good spot,” Helsley said. “Definitely helped a lot going into the offseason and getting ready to come into spring. If they want me to close, I’ll be ready for it.”

Junior Fernández

Fernández is still a rookie and faded some from the closer conversation in Spring Training. He went 0-for-3 in save opportunities last season, with a 5.40 ERA in 11 2/3 innings across 13 games. The Cardinals could let him pitch his way into save opportunities, with the logic that the better he pitches, the higher-leverage situations he pitches in.

Maddux also said there’s a chance that some of the pitchers stretched out -- like Gomber and Ponce de Leon -- who can throw multiple innings could emerge for the ninth. Both have swing-and-miss pitches for late-inning situations.

“A combination like that is viable,” Maddux said. “And the score will tell us what to do in that regard.”