My grandpa often tells me a story from the 1930's when St. Louis starting pitcher Bud Parmelee (Roy Parmelee) first faced his former team, the New York Giants. As you can imagine, Parmelee was a competitive guy who really wanted to beat his former team more than anyone; and he actually made it through the first seven innings with little or no problem--and a 1-0 lead. But he could tell he was tiring by the time the 8th inning rolled around. Common sense said it was time for a call to the bullpen, but Parmelee was a man on a mission and he took the mound in the 8th inning...
As my grandpa relates the story, Parmelee's tiring arm was obvious in the 8th as the opposing hitters crushed ball after ball... to the warning track for lucky outs. However, Parmelee's luck ran out in the 9th inning as he walked the bases loaded, nobody out, and a one-run lead. The Cardinals made a call to the bullpen and brought in none other than Dizzy Dean.
Parmelee felt terrible that he had let his new team down. He hung his head and handed the ball to Dizzy, but Dizzy just patted him on the back and said, "Don't worry, you won the ballgame." Dizzy then proceeded to strike out the next three batters for the win.
I always liked that story for various reasons. First off, I can relate to wanting to beat your old teammates; second of all, the story has a struggle, a hero, and a happy ending. It's great.
But the bigger issue at hand is having a pitcher who you can trust with the game on the line. There really aren't many pitchers like that in baseball today. Yeah, every team has a closer. But seriously, not every team has a closer.
For my money, Jonathon Papelbon and Joe Nathan are the two best closers in baseball. Although, I also like Bobby Jenks in a playoff situation (you gotta respect a World Series champion). In the end, I give the edge to Papelbon. He's got the stuff, the experience, and a proven plan to stay healthy.
Note: From a fantasy standpoint, it's a tougher call. Part of Papelbon's health regimen is to not pitch more than two or three games in a row. As a result, he will rack up fewer saves and strikeouts than he otherwise could.