The Mets are off to a red-hot start in 2018, opening the season 7-1 after a weekend sweep of the division rival Nationals in Washington.A big reason why New York has surged out of the gate is a stellar performance from its bullpen, which has posted a 1.31 ERA (five

The Mets are off to a red-hot start in 2018, opening the season 7-1 after a weekend sweep of the division rival Nationals in Washington.

A big reason why New York has surged out of the gate is a stellar performance from its bullpen, which has posted a 1.31 ERA (five earned runs in 34 1/3 innings) from Opening Day through Sunday, earning MLB Bullpen of the Week presented by The Hartford for the period from March 29 through April 8.

As part of the Hartford Prevailing Moments program, each Monday throughout the 2018 season, MLB.com is honoring the Bullpen of the Week. An industry-wide panel of MLB experts, including legendary stats guru Bill James, constructed a metric based on James' widely renowned game-score formula, to provide a weekly measurement of team-bullpen performance.

Here's how the Bullpen Rating System is compiled for each week. For reference, a weekly score of 100 is considered outstanding:

• Add 1.5 points for each out recorded

• Add 1.5 points for each strikeout

• Add 5 points for a save

• Subtract 2 points for each hit allowed

• Subtract 4 points for each earned run allowed

• Subtract 2 points for each unearned run allowed

• Subtract 1 point for each walk

• Subtract 5 points for a blown save

The Mets' bullpen finished with a score of 170 after seven strong innings in Sunday's 6-5 victory over Washington in 12 innings. Overall, four of New York's relievers have yet to give up a run this season, with Seth Lugo (6 innings), AJ Ramos (4 1/3), Jerry Blevins (1 2/3) and closer Jeurys Familia (6 innings) boasting pristine zeros in the run department.

The unexpected: On Sunday night, starter Matt Harvey exited after five innings, giving up four runs on nine hits against the Nationals. Little did the Mets know just how much they'd need out of their relief corps in a game that would go 12 innings on a very cold night in Washington. Robert Gsellman was the first reliever out of the 'pen, and after tossing a scoreless sixth, gave up a run on a Michael Taylor RBI single in the seventh that tied the game at 5.

How they prevailed: Ramos, Blevins, Lugo and Jacob Rhame combined to surrender only two hits over the final five innings to hold the Nats scoreless while Yoenis Cespedes drove in the go-ahead run in the 12th with a single. In the bottom of the 12th, Rhames retired Matt Reynolds and Pedro Severino , but then gave up a double to Wilmer Difo . With the tying-run at second, Rhames induced a game-ending ground out from Adam Eaton to seal the victory for New York.

The Mets edged the Cubs, who had a very strong bullpen performance of their own to open the 2018 campaign. Chicago finished second, with a score of 163.5. The Angels' relief corps finished third, with a score of 145.

Manny Randhawa is a reporter for MLB.com based in Denver. Follow him on Twitter at @MannyOnMLB.