LAKELAND, Fla. -- With less than a week to go before rosters must be finalized, the Detroit Tigers’ bullpen picture remains a murky one -- amorphous and ever-changing even as the days of spring training dwindle.

Much of how the remaining few spots will shake out hinges on the team’s relative health. Alex Wilson, who has been hampered by a lat strain all through camp, has been ruled out for Opening Day, and his fellow reliever Blaine Hardy appears likely to earn a similar designation.

Manager Brad Ausmus did not sound confident on Sunday when assessing Hardy’s potential availability when the club begins the regular season on the road in Miami against the Marlins on April 5.

“With every passing day, I’ve become less and less confident he’s going to be ready,” Ausmus said.

The back end of the bullpen appears to be set with closer Francisco Rodriguez and offseason additions Mark Lowe and Justin Wilson expected to handle setup roles. But the front end presents a much more intriguing competition, with Drew VerHagen appearing to be the only incumbent locked into a spot. The situation remains fluid -- with Hardy’s question mark a big reason -- with the likes of Bruce Rondon, Kyle Ryan, Buck Farmer, Lendy Castillo and Bobby Parnell all competing for just a few available openings.

Add Shane Greene to that mix, as well, should the Tigers keep Matt Boyd as the fifth starter and use Greene in long relief.

The Tigers, hell-bent on adding depth and fostering competition, came into camp with a crowded bullpen. And even as injuries have thinned out the corps, the club has yet to determine who exactly will be with the team once the Tigers begin the season and subsequently head north to Detroit. Ausmus would prefer to make these decisions soon.

“It’s gotta get done sooner than later. There’s only a week left,” Ausmus said after Sunday’s game. “It’ll be decided here in short order. It’s not going to go down to the last game of the spring or anything like that. But decisions haven’t been finalized at this point."

Parnell was the only one to help his cause on Sunday in the Tigers’ 8-3 loss to the Houston Astros, as the former Mets closer delivered his strongest outing to date since signing with the team as a free agent before camp.

Parnell recovered from a leadoff double in the ninth and retired three straight batters, striking out two.

“I thought that was his best outing, quite frankly,” said Ausmus, who noted Parnell finally let the ball go, rather than aiming like in previous appearances.

The 31-year-old reliever, who had Tommy John surgery in 2014, has been encouraged also by his increasing velocity. Earlier this spring he was throwing in the low 90s, and now he's throwing upwards of 96 mph. There is some hope still that his velocity could continue to improve.

“It wouldn’t shock me, the way he’s been trending, if in another month, he was throwing 96 to 98 [mph] consistently,” Ausmus said.

Regardless of his velocity, Parnell feels his confidence is growing and the faith in his arm strength has been restored. Whether that will add up to him carving out a spot on the club’s big league roster remains to be seen.

“I feel like I have a chance,” said Parnell, who has an opt-out clause in his minor league contract. “I feel like I can help the bullpen, when things are good, but like I said, I need to be more consistent. I don’t know what they’re thinking but I’m gonna keep working to make things better and if they feel like I can help the bullpen, I’ll be there to help them. If not, I’ll keep working.”

Conversely, it was a bleak day for both Castillo and Rondon, who struggled in their respective appearances against the Astros.

Castillo walked three batters and Rondon gave up two home runs in 2/3 of an inning.

Castillo has been a pleasant surprise in camp for the Tigers this spring -- the former shortstop was not expected to be among those competing for one of the last spots -- but Rondon’s trajectory has taken some maddening twists and turns. Logan Kensing has also made a favorable -- albeit unexpected -- impression.

Rondon has pitched lights-out while hitting triple digits on the radar gun, but he has gotten lit up on a few occasions, as well. Last season’s maturity issues notwithstanding, Rondon’s lack of consistency remains the most immediate area of concern for the organization.

And right now, it is his biggest hurdle to clear if he wants to make the team.

“There’s no magic formula,” Ausmus said. “He needs to pitch well.”