There have been many great closers in the history of baseball. Some of them have been Mariana Rivera, Derek Lowe, and Keith Folke. Mariana Rivera is won of the best closers around right now. In  clutch situations he comes through. In 25 and 2-3s innings of post season play he hasn't gave up a run!!! In 18 post season appearances he's had 12 saves and has won 2 games as a closer in 1999. His ERA in the playoffs is 0.36 in 47 and 2-3s innings giving up only 2 earned runs the the lowest for any pitcher with at least 30 innings in post season history. Derek Lowe is another great closer. He won the Cy Young award in 2003. Lowe last year threw a seven inning three hit shutout to help Boston win 3-0 in the  Nationals League champion. Another great closer is Keith Folke. He hasn't done to well this year. He's 1 and 3 with a 7.20 ERA. Keith Folke helped the Red Soxs win game 7 of the American League Championship. He threw seven innings, gave up three hits, one walk, and struck 4 people out pitching his best.  Folke also has earned the victory in relief of Game 3 of the Division Series, and has been  the winning pitcher in all three of Boston's post season clinchers.