Jason Grilli and Mark Melancon (USATSI)
Jason Grilli (left) and Mark Melancon (right) have been untouchable for the Pirates. (USATSI)

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Following Thursday night's 7-1 win over the Brewers, the Pirates are 18-0 when leading after seven innings this season. Pittsburgh is 24-17 overall, tied for the third-best record in the NL, and the team's ability to preserve those late leads is a huge reason why.

The reason behind that 18-0 record when leading after seven innings is rather simple: setup man Mark Melancon and closer Jason Grilli have been dominant. Grilli leads baseball in saves (16) while Melancon leads baseball in holds (14), but those stats are a function of opportunity more than anything. The other 23 players on the roster create those save and hold opportunities for Grilli and Melancon, respectively. They don't tell enough of the story.

Pittsburgh's two late-inning right-handers have combined to allow just three runs this year. Melancon coughed up a solo home run to Joey Votto on April 14 while Grilli surrendered an RBI double to Carlos Beltran on April 27 and an RBI single to Mike Baxter on May 9. That's it. One-fourth of the way through the season, those two have allowed the same number of runs Fernando Rodney allowed on Thursday night alone.

Melancon and Grilli have been so dominant this year that only one other setup man-closer combination in the game comes close to their performance, at least in terms of the WAR (FanGraphs version):

2013 Combinated Setup Man & Closer Stats
Team Pitchers IP ERA WHIP WAR
Pirates Grilli & Melancon 38 2/3 0.70 0.72 1.6
White Sox Addison Reed & Jesse Crain 37 1.70 1.16 1.6

Only three other clubs -- Diamondbacks, Twins and Blue Jays -- have a closer and setup reliever who combine for more than than 1.0 WAR at the moment. Mariano Rivera and David Robertson aren't there yet, neither are Aroldis Chapman and Jonathan Broxton, Ryan Cook and Grant Balfour, Rafael Soriano and Tyler Clippard, or any of the game's other top closer-setup man combos.

Grilli, 36, was excellent while serving as Joel Hanrahan's setup man from 2011-12, pitching to a 2.76 ERA with 12.5 K/9 in 91 1/3 innings. That performance not only earned him a two-year, $6.75 million contact over the winter, it also earned him the closer's job. The Pirates traded Hanrahan to the Red Sox and handed Grilli the ninth inning.

The 28-year-old Melancon was part of the trade return for Hanrahan. He had a strong year for the Astros in 2011, saving 20 games in 25 chances with a 2.78 ERA, but was terrible early on with Boston in 2012. They sent him to the minors with a 49.50 ERA after four appearances, but Melancon returned in June and pitched to a much more respectable 4.19 ERA the rest of the way.

The Pirates had the best bullpen WHIP (1.13) and third-best bullpen ERA (2.82) in baseball entering Friday. Grilli and Melancon are the backbone of their relief corps, preserving every lead that has come their way. No team has received better work from their closer and setup man a quarter of the way through the season, and the duo is a big reason why only a few have better overall records than the Bucs.