It's best not to overreact to what happens over a small sample at the beginning of the season, but when performance affects roles, fantasy owners need to pay attention. This is best illustrated with closers, who as a whole have gotten off to a terrible start in 2012. Here are the situations currently most tenuous:
Rays: Tampa Bay swept the Yankees, and Fernando Rodney picked up a win and two saves in the process. With Kyle Farnsworth out at least the next 4-to-6 weeks, whoever closes for the Rays will hold plenty of fantasy value, but all signs point to a committee. Rodney looks to be the favorite for now, and he does have closer "experience," but he also had an ugly 26:28 K:BB ratio last year and has a career 1.46 WHIP. Joel Peralta is off to a rough start but is the superior pitcher, although manager Joe Maddon is smart, which might lead to Peralta being used in higher leverage situations while Rodney is saved for the easier role in the ninth inning.
Red Sox: After losing Jonathan Papelbon to free agency and Andrew Bailey to injury, Boston's bullpen has been an absolute disaster to open 2012, especially the back end. Mark Melancon and Alfredo Aceves combined to allow the winning run in the bottom of the ninth during the team's season opener, but that was nothing compared to Sunday, when they allowed a combined six runs while recording just two outs.
Aceves, who was named the closer before the season started, has a career 1.10 WHIP but with just so-so peripherals – 2.3 K:BB ratio, 6.3 K rate – and is unlikely to get Boston's next save opportunity. The team may look outside the organization for help, and the preferred fantasy option right now very well may be Daniel Bard, who could soon be moved back to the bullpen.
White Sox: While most fantasy owners drafted Matt Thornton, Addison Reed and possibly even Jesse Crain, Hector Santiago was given the team's first save chance and has since been confirmed as Chicago's closer. It's not totally out of nowhere, as new manager Robin Ventura hinted as much, but it's somewhat surprising, as Santiago's numbers in the minors throughout his career are underwhelming, highlighted by a 4.1 BB/9 rate.
The left-hander's screwball can be effective against righties, and it's often best not to pigeon-hole your best reliever in the closer's role, but Thornton, who had a 31:6 K:BB ratio and a 0.99 WHIP after the All-Star break last season and Reed, who had a 12.9 K/9 rate throughout the minors, are both likely to perform better, which could eventually lead to a change. Thornton owners need to remain patient.
Indians: After missing most of spring training with an oblique injury, Perez allowed three runs in a blown save during the season opener. He's since recorded two scoreless innings and secured a save, but his job can't be all that secure. Despite approaching 40 saves last season, Perez had a 39:26 K:BB ratio over 59.2 innings, and he has Vinnie Pestano breathing down his neck. Pestano came out of nowhere last year, and we see middle relievers do this all the time and be unable to repeat it, so he's no sure thing himself, but with an 88:24 K:BB ratio over his last 64.2 innings, it's hard not to argue he's the superior pitcher right now.
Nationals: Drew Storen's tender elbow continues to be more worrisome, and there's a real chance he misses a significant amount of time this season. As a result, Washington appears to be using a committee to close games, featuring Brad Lidge and Henry Rodriguez. Both are wild cards, as Lidge hasn't thrown 60.0 innings in a season since 2008, while Rodriguez has a 5.58/9 career walk rate. Lidge does appear to be healthy, and Rodriguez has averaged 98.6 mph with his fastball this season, so on an improving Washington team that projects to win around 85 games, both are obviously worth owning in fantasy leagues.
Cubs: Carlos Marmol saw his K rate drop from 15.99 in 2010 to 12.04 last year, and while the latter is still fantastic, his career walk rate of 5.92/9 remains a real problem. He's allowed three runs and seven baserunners without a strikeout over 1.1 innings so far this year, already recording a loss and a blown save in two of the team's three games. Marmol has thrown the third-most pitches among all relievers over the past six seasons since entering the league, and no hurler in baseball relies more on a slider, so he carries both health and performance risk.
Kerry Wood has been nearly as bad early on this season and would be unable to go three days in a row if he were to take over the closer's role. Despite the poor start to the year, Wood would likely get the first chance at the job if Marmol were to lose it, but Rafael Dolis is the real sleeper in Chicago's pen and should be stashed in deep mixed leagues.