Every year in the postseason, we become well acquainted with each team’s ace starters, clutch hitters, defensive wizards, or gritty closers called in to save a game that could decide the fate of the season. Yet it seems that more often than not, the important games are decided not by these traditional heroes, but by virtually unknown middle relievers. These players have the far less glamorous – but no less important – job of handing a lead off to the closer.

The following relief pitchers may not get much media coverage, but they are just as valuable to their teams as their more famous teammates.

To reach the postseason, the Chicago White Sox depended heavily on righty Cliff Politte, who stands just 5-foot-10 but manages to throw a 98 mph fastball. He mixes that four-seamer with a two-seam sinking fastball and a hard slider, and the results this year have been outstanding. In 67.1 regular-season innings, Politte struck out 57 and had a 2.01 ERA.

For most of the year, Politte has been used to shut down rallies already in progress. In his 68 appearances, Politte inherited 51 base runners, yet allowed only 11 of them to score. An average reliever in the major leagues would have allowed about 23 of those runners to cross the plate. Only one pitcher in baseball has stranded more runners than Politte.

This is a good example of how traditional statistics fail to measure the more nuanced points of baseball. Since those stranded runners were put on base by a previous pitcher, ERA doesn’t give Politte credit for preventing them from scoring. Baseball Prospectus has developed a statistic called Fair Runs Allowed to account for the fact that some relievers are especially good at shutting down rallies, or are especially unlucky with the runners they leave to the next pitcher. In this adjusted statistic, Politte was the best reliever in all of baseball in 2005 and had the fourth best season in the last 15 years.

So far this postseason, Chicago’s starters have put together long and successful outings – including four straight complete games to reach the World Series. This is historic baseball: The last team to get four straight complete games from their starters in the postseason was the 1956 Yankees. It would be unprecedented for the White Sox starters to maintain this record of dominance. You can be certain that Politte will get crucial innings in the World Series, and his 2005 track record suggests he’ll be up to the task.

The Angels turned over many of their high-leverage innings this year to Scot Shields, a converted starter who works with a sneaky 90 mph fastball as well as an average curve, slider, and change-up. Shields put together an excellent record this season: 2.75 ERA, 98 strikeouts versus only 37 walks, and a miniscule 0.49 home runs allowed per nine innings.

His 91.7 relief innings pitched were the second most in all of baseball. In an era when many of the best relievers are used sparingly, Shields helps manager Mike Scioscia by always being ready to throw. Whether it’s a multi-inning outing or the third day in a row that he’s been used, Shields’s rubber arm gives the Angels a solid relief option no matter the situation.

Just look at his playoff numbers this season. Shields threw in four of five ALDS games against the Yankees (notching a 3.60 ERA overall and only faltering in his fourth outing). In the ALCS, he was used to protect a lead and the win in Game 1, then pitched three more times when Angel starters struggled early in the following games. The last three games were L.A. losses, but not because of Shields: He threw six innings of shutout ball in four games and lowered his postseason ERA to 1.64 in 11 innings.

It always seems that the Astros are developing hot young closers. When the team depended on lefty fire-baller Billy Wagner, Octavio Dotel was waiting in the wings. When Dotel was handed the closer’s job, Brad Lidge was promoted to setup man. Now that Lidge is the closer, the crucial middle relief innings fall to Dan Wheeler, a right-hander who bounced through three organizations before landing with Houston. This year, in 73.3 innings, Wheeler has struck out 69 and walked only 19, posting a 2.21 ERA.

Another statistic Baseball Prospectus uses to rate relievers is Adjusted Runs Prevented (ARP). Essentially, ARP looks at the specific outings a pitcher is thrown into and counts the number of runs the reliever in question prevented versus what an average pitcher would have allowed. Wheeler’s 2005 ARP of 22.5 was the 15th best mark in all of baseball, and it was 5.6 runs better than closer Brad Lidge’s mark this season.

Wheeler threw a mop-up inning in Game 1 of the NLDS against the Braves and came back in Games 3 and 4. In the classic 18-inning final game of the NLDS, Wheeler threw three shutout innings and handed the ball to Roger Clemens for the win. He wasn’t needed in the first three games of the NLCS, but in Sunday night’s controversial win over St. Louis, Wheeler took the ball with a one-run lead in the eighth and shut the Cardinals down. His postseason ERA now stands at 1.69 with 5.1 innings pitched, and if the Astros can close out St. Louis (they were up 4-2 in the eighth inning of Game 5 last night when this edition of The New York Sun went to 1171 2094 1320 2106print), Wheeler will certainly get many more clutch innings in the Fall Classic.

Speaking of the Cardinals, middle relief is one area where the defending NL champs have struggled this postseason. There’s a simple reason. All year, the team depended heavily on 34-year-old righty Al Reyes. His 2005 ARP was 24.0,6.9 runs better than closer Jason Isringhausen’s season mark. He prevented a solid 8.9 inherited runs from scoring and finished the season with a 2.15 ERA in 62.7 innings, with 67 strikeouts against only 20 walks. But alas, Reyes blew out his elbow on the final day of the regular season.

Everyone in the bullpen (except Isringhausen) has been forced to assume a new role, and the results haven’t been pretty. In the NLDS, the St. Louis bullpen allowed eight runs in just 8.1 innings. Julian Tavarez, who has taken most of Reyes’s important innings, has a postseason ERA of 10.80. Reyes is exactly the pitcher you would have expected in the later innings of Sunday night’s controversial loss to the Astros, but instead Jason Marquis was thrown into the game and served up the losing run. If the Cardinals don’t make the World Series, significant responsibility has to be laid at the feet of their frazzled middle relievers.

Mr. Gorman writes for Baseball Prospectus. For more state-of-the-art commentary, visitwww.baseballprospectus.com.