The job of closer might be the most fluid gig in baseball.
Sometimes a team heads into a season with grand plans for its ninth-inning guy and then sees him blow up in the first two weeks of April.
That's when creativity is needed in a hurry, so there go the bullpen doors and here comes the former setup man. Triple-A closer, veteran on a Minor League contract or converted former starter. Or, really, anyone who can get three outs in the ninth inning.
In other words, it's become increasingly evident that it's difficult to know who can and who can't close games in a given year -- or month or week, for that matter -- which makes this time of year difficult and unpredictable for players with closer resumes but large contract demands.
As the high volatility of the role has seemed to increase over the years, the willingness to invest huge dollars and years into one inning seems to shrivel.
So what will happen this offseason? Here's a look at 10 of the most prominent free-agent closers and some intriguing alternate contenders:
Joe Nathan, RHP: Nathan will turn 39 later this month, but he seems as young as ever. His season with Texas was simply spectacular, with a 1.39 ERA, a WHIP of 0.90, 43 saves and 73 strikeouts in 64 1/3 innings. That could get him a multiyear deal.
Brian Wilson, RHP: If he's healthy and reaching the mid to upper 90s with his fastball after coming back from his second Tommy John elbow reconstruction surgery, the veteran Wilson is one of the best options in this group. He pitched to a 0.66 ERA with 13 strikeouts in 13 2/3 innings down the stretch of the regular season as a setup man for the Dodgers, and then threw struck out eight in six scoreless innings in an excellent postseason stint. That's a small sample size, though.
Grant Balfour, RHP: Balfour will turn 36 in December, but he still hits 93-94 mph with his fastball and has posted ERAs ranging from 2.28 to 2.59 in each of the past four seasons with healthy strikeout-to-walk ratios.
Fernando Rodney, RHP: Rodney's fastball still reaches 100 and his changeup remains one of the best around. Naturally his 2013 season wasn't going to be as good as his otherworldly 2012, but he did strike out 82 batters in 66 2/3 innings and saved 37 games.
Joel Hanrahan, RHP: Toss out his 2013 season, which was cut short because of Tommy John surgery. He was such a good closer for Pittsburgh that the Red Sox traded Mark Melancon and three others for him and Brock Holt. It's never easy to predict how long it will take a pitcher to come back from elbow surgery and how effective they'll be when they do, so Hanrahan might have to agree to an incentive-laden one-year deal.
Kevin Gregg, RHP: The internal numbers aren't spectacular, but Gregg saved 33 games this year and his experience and know-how mean something to Major League teams.
Rafael Betancourt, RHP: Betancourt finally made a name for himself as a ninth-inning man in 2012, but injuries robbed him of an opportunity to continue in the job with Colorado for much of 2013. He's 38, so he'll need to prove he's healthy in order to get solid offers this winter.
Chris Perez, RHP: Perez calls himself "Pure Rage," and he had a trying season with the Indians, including arm troubles, legal troubles, and ultimately, ninth-inning troubles that led to him being replaced in the closer role and then released. Perez is 28 and has good strikeout numbers and a live fastball, so he might garner some interest.
Joaquin Benoit, RHP: Benoit had never been a full-time closer prior to the middle of this season, and he earned 24 saves while pitching to a 2.01 ERA. People might forever remember the changeup that David Ortiz hit out of Fenway Park for a game-tying, postseason-altering grand slam in the American League Championship Series, but Benoit has been one of the AL's better relievers for a while, and that didn't change this year.
Edward Mujica, RHP: Mujica saved 37 games for the National League-champion Cardinals, pitching to a 2.78 ERA and 1.01 WHIP. Then October arrived, and Mujica, who had an 11.05 ERA in September, watched as young Trevor Rosenthal took over to finish games while Mujica threw a total of two inconsequential innings. He's 29, so a change of scenery might be the ticket.
Other possibilities: David Aardsma, RHP; Joba Chamberlain, RHP; Jesse Crain, RHP; Frank Francisco, RHP; LaTroy Hawkins, RHP; Brandon Lyon, RHP; Ryan Madson, RHP; Carlos Marmol, RHP; Brett Myers, RHP; Manny Parra, LHP; Oliver Perez, LHP; Matt Thornton, LHP; Francisco Rodriguez, RHP; Jose Valverde, RHP; Jose Veras, RHP.
Doug Miller is a reporter for MLB.com. Follow him on Twitter @DougMillerMLB.