Out of all 25 players on an active MLB roster, perhaps the toughest position to consistently fill is the closer role. Although the closer only appears for one inning every game, that inning is filled with stress, pressure and the eyes of every fan in the stadium and at home, waiting to get the final three outs of the game.

For about 17 years, the best closer in baseball has been Mariano Rivera of the New York Yankees. Rivera has led the majors in saves three times (’99, ’01 and ’04) and has made the All Star team 13 times in his 19 seasons with the Yankees.

Despite dominating opposing teams at age 43 this season, recording 35 saves in 45 appearances, this will be the last year for Rivera who is retiring. This will leave a huge hole in the majors, at a time when most ball clubs have a difficult time finding someone to finish games off for them on a consistent basis year-in and year-out.

But there are four quality candidates who could take over Rivera’s mantle as the best closer in baseball not only for the 2013-14 season but for the foreseeable future.

4. Joe Nathan, Texas Rangers

At 38 years old, Nathan may not be around for much longer. But while he is still in the majors he can be a shutdown closer. Nathan, in his 13 years as a pitcher, has spent time with the San Francisco Giants, Minnesota Twins and most recently the Texas Rangers. During his two years with the Rangers, Nathan has converted on 93.5 percent of his save chances, according to Baseball Reference, and currently is fourth in the league with 33 saves.

Since becoming a full-time closer with the Twins in 2004, Nathan has never converted less than 36 saves in a season when he appeared in 64 or more games. Despite Nathan’s 90 percent career conversion rate, his age will likely prevent him from becoming baseball’s elite closer.

3. Joe Johnson, Baltimore Orioles

Johnson is my no means a perfect closer, but he does have enough talent that if he can avoid some of the breakdowns he’s encountered thus far in his career he could become the big league’s best closer. Johnson is leading the league in saves this season, but has blown six saves in 54 appearances for a 87 percent conversion rate on save chances.

However, if he can turn it around this season heading into next year and return to the form he had during the 2012 season when he converted 94 percent of his save chances and led the league with 51 saves Johnson is a force to be reckoned with. When Johnson is on, he’s on, only walking seven percent of the batters he’s faced on his career and striking out 18 percent of opponents this year, according to Baseball Reference.

At 30, Johnson still has time to make some minor improvements, and as the Orioles continue to improve Johnson will be the one saving the games for this young Baltimore team.

2. Jason Grilli, Pittsburgh Pirates

Like Nathan, Grilli’s age could turn out to be a factor in the coming years. Grilli is currently serving a stint on the disabled list at the age of 36, playing on his sixth major league team. Grilli seems to have found a home with the budding Pirates, converting on 30 of his 31 save opportunities.

The former starting pitcher came on as a reliever with the Detroit Tigers in 2005, but didn’t become a full time closer until this season. Most fans will take away value from Grilli due to his lack of experience as a closer, but if he can keep up the pace he had this season before going on the DL there’s no reason why he couldn’t be leading the league in saves this time next year.

1. Craig Kimbrel, Atlanta Braves

The fourth-year player has the perfect combination of potential and current success to have the best chance to claim the title of the best closer in baseball. At only 25, Kimbrel has already led the league in saves twice and is only three saves behind Johnson for the current league lead. Last season, when Kimbrel recorded 42 saves, he finished with a 1.01 ERA in 63 appearances.

In Rivera’s 17 years as a closer in New York, the only time he got close to an ERA like that was in 2008 when he finished the year with a 1.40 ERA in 64 games. Numbers aside, Kimbrel is the closer that when he comes in the ninth inning with the Braves in the lead, fans of the opposing team start to file out the stadium, knowing their team won’t be winning the game that night. Kimbrel did stumble out of the gate in 2001 when he had eight blown saves but only has six blown saves since then.

Between his 44 percent career strikeout percentage and 0.919 career WHIP, there’s no doubt that Kimbrel will be the best closer once Rivera retires.