Relievers are tricky as a species, and the group of free agents for 2015-16 are no different. Most of them have flaws of some kind. Perhaps they don't throw hard as the classic stopper, or they have multiple Tommy Johns in their past, or they're vulnerable to right- or left-handed batters. Or they don't have experience in "save" situations. A year ago, perhaps 11 free-agent relievers had experience as a closer; this season, perhaps five or six have histories as closers, and only three or four closed games in 2015. That doesn't mean teams can't find value out there if they look hard enough. Let's take a look at the field:

1. Darren O'Day

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O'Day -- he's a sidewinder. (USATSI)

Since the 2012 season began, few relief pitchers have been as tough to beat as O'Day. Only seven relievers in the majors who have pitched at least 200 innings since '12 have allowed a lower adjusted on-base plus slugging percentage. That means, relative to the rest of the league and the home ballpark, batters don't get on base, and they don't hit for much power against O'Day. All of the relievers ahead of O'Day on the list are full-time closers except for Jake McGee, who closes sometimes. O'Day has accumulated only 12 saves in that span, which is likely to affect how much money he gets in free agency. But if someone offers him "closer" money, don't expect him to stay in Baltimore. It's an awkward situation for O'Day, who is appreciative of his time spent in Baltimore with manager Buck Showalter but also realizes the Orioles won't allocate those kinds of resources for him when they already have Zach Britton in the bullpen.

"Darren has enjoyed tremendous success the last four years in Baltimore," his agent, Jeff Borris, told Eye on Baseball. "He has loved pitching for Buck and has been treated great by the fans of Baltimore. But naturally, with a thin free-agent class of relievers, he has drawn the interest of many teams."

In terms of getting batters out, he's one of the best in the majors. O'Day, who is 33, has lowered his ERA every year since 2012 and posted a career-best 11.3 K/9 and 5.86 K/BB ratio in 2015. Dominant against righties, O'Day has worked to be better against left-handed batters. Over the past two seasons against lefties, he is comparable to Jonathan Papelbon and Huston Street, and more effective than Kenley Jansen and Jeurys Familia. He could be given a shot to close somewhere but, at the worst, he is an excellent right-on-right matchup guy.

2. Joakim Soria

Soria was more home run prone than ever before this past season (1.1 HR/9) and at age 31 with two Tommy John surgeries in his history, it could be the new normal rather than a blip. Soria still misses bats (8.5 K/9) and is a capable late-inning arm, though he has been more hittable since returning from his second elbow reconstruction in 2013. Still, he was 23 of 26 in save opportunities with the Tigers, which is consistent with his 88 percent career mark. Given the weak market, he'll probably get three-year offers at about $6 million per, but could do better with a short-term deal for a team wanting to make him the closer in 2016.

3. Mark Lowe

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Impressive sideburns as well. (USATSI)

In the first part of 2015 with Seattle, he pitched the best ball of his career at age 32 years (32.6 K%, 7.6 BB%, .612 OPS), and was mostly as good for the Jays except for a blip here or there at the beginning after a deadline trade. He might be the best power arm on the market, all things considered.

4. Ryan Madson

After missing the 2012-14 seasons following Tommy John surgery and various complications, Madson returned in 2015 and gave the Royals 63 1/3 innings with a 2.13 ERA (195 ERA+). He got stronger as the season progressed as well, finishing with the 20th adjusted OPS among relievers who pitched at least 40 innings. Madson might not get multiple years at age 35, but he could be in line for a nice guaranteed payday on a one-year contract. Has a history as a closer and, thanks to the Royals, the always-welcomed World Series Experience.

5. Tyler Clippard

A two-time All-Star since 2011, he didn't pitch as well in 2015 as his 2.92 ERA and 19 saves indicate. His strikeout percentage dropped from 29.5 to 19.4. His walk percentage was its highest in five years, as was his line-drive percentage. His .599 OPS against was better than his career average, and he was great against left-handed batters. He turns 31 in February.

6. Tony Sipp

The Astros picked Sipp up off the scrap heap in May 2014 and he gave them 105 innings with a 2.66 ERA (149 ERA+). Sipp has managed to cut his walk rate (2.5 BB/9 in 2015) while maintaining a huge strikeout rate (10.3 K/9). He posted a .599 OPS against lefties, similar to Andrew Miller, though Javier Lopez (.323) and Zach Britton (.325) led the league. A relatively new changeup has allowed him to better combat righties. He could be be a surprising bargain this winter.

7. Shawn Kelley

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Might be your best value here. (USATSI)

He has compiled 201 strikeouts over his past 156 1/3 innings in the past three seasons. His OPS against has dropped from .729, to .663, to .596. His fielding independent pitching is dropping, too. He's more vulnerable to left-handed power, but not alarmingly so. He turns 32 in April

8. Trevor Cahill

It was just 17 innings, but he was terrific for the Cubs in relief posting a .494 OPS against, a 2.12 ERA and a 22-to-5 strikeout-to-walk ratio. He turns 28 in March, which is another plus, after six seasons of mostly unfulfilled promise. An All-Star who finished ninth in Cy Young voting in 2010, his career +98 ERA in 1,083 2/3 innings isn't exciting. It all depends on how you want to look at him. Did the Cubs finally tap his potential? Is his success from 2015 repeatable? Can he still be a starter? There figure to be plenty of teams interested, it's just a matter of how much they're willing to offer.

9. Antonio Bastardo

He limited lefties to a .448 OPS. His strikeout percentage (26 percent) is trending downward, but so is his walk percentage and his extra-base hit percentage. More vulnerable against righties, but not alarmingly so. Not much difference between him and Sipp, though Bastardo is two years younger.

10. Tommy Hunter

Been around the block as a starter and reliever, but won't turn 30 until July 3. Posted back-to-back excellent seasons as set-up guy/part-time closer with Orioles in 2013-2014, but regressed some in 2015. His 19.4 percent with strikeouts over the past three seasons isn't ideal for the back of the bullpen. Allowed a .457 slugging percentage to left-handed batters.

The next five: Jonathan Broxton, Fernando Rodney, Franklin Morales, Blaine Boyer and Neal Cotts. Five after them: Joe Thatcher, Carlos Villanueva, Casey Janssen, Matt Thornton and Matt Albers.

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Blaine Boyer picked a great year to post a 2.49 ERA. Also, Ho-ho-ho! (USATSI)