Wednesday night in Pittsburgh, the Pirates beat the Diamondbacks (PIT 5, ARI 4) for their 3rd straight win and their 8th win in their last 10 games. The Buccos are 26-19 on the season. They're five games back of the Cubs in the NL Central.

The Pirates beat the D-backs on Wednesday thanks to their star-studded outfield. The trio of Andrew McCutchen, Gregory Polanco, and Starling Marte went a combined 5 for 12 with a double, a stolen base, two runs scored, and two runs driven in. That's on top of their typically excellent defense.

At a combined +6.3 WAR per FanGraphs, the Pirates have baseball's best outfield this season, and when you break it down, it really isn't all that close. The Cubs are second at +6.1 WAR but so much of that is defense (11.8 runs saved), and defensive stats are still pretty unreliable, especially in 40-something game samples.

The Pirates outfield has done well defensively (4.3 runs saved) but they blow the Cubs and pretty much every other team out of the water offensively. Weighted runs created plus, or wRC+, says Pittsburgh's outfield has been 43 percent better than league average offensively when adjusted for ballpark and things like that. The Marlins are second at 38 percent better than average and no other team is more than 25 percent better than average. That's a big gap.

Obviously the Pirates outfield is led by McCutchen, a bonafide superstar and former MVP, right? Well yes, right. He's the household name. Except he has been only the third best player in the team's outfield this season. Both Marte and Polanco are outproducing McCutchen. Check it out:

PA AVG/OBP/SLG OPS+ HR RBI SB WAR
Polanco 195 .317/.402/.557 159 6 29 7 +2.4
Marte 181 .318/.359/.453 120 3 17 14 +1.8
McCutchen 200 .258/.340/.461 116 8 20 1 +1.1

The Pirates signed Polanco to a five-year extension worth $35 million last month and wow does that already look like a bargain. He's breaking out as a star offensively this season in addition to being a very good defensive right fielder.

Given his track record, it's fair to expect McCutchen to hit quite a bit more going forward this season. He's gotten off to a slow start in 2016 relative to his lofty standards. At the same time, Polanco's performance may take a slight step back, which doesn't mean he'll be bad, just not so outrageously good. Marte's numbers are right in line with what he's done since becoming a full-time player in 2013.

Including option years, the Pirates have Polanco under contractual control through 2023 and Marte through 2021. McCutchen is under control through 2018, so these three are going to be together for a few more years too. They've been the best outfield in the game in 2016 and they figure to continue being baseball's best outfield for the next few seasons as well.

The Pirates are certainly not a perfect team -- the could use some pitching help more than anything, especially at the back of the rotation -- but their outfield is the best in the business. It's the backbone of a club that has now gone to the postseason the last three years and expects to play in October again this year.

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Marte, McCutchen, and Polanco have been baseball's best outfield so far this season. USATSI