On Tuesday night, ESPN's David Schoenfield posited an interesting question on Twitter: Is the Tampa Bay relief combo of Jose Alvarado and Diego Castillo the best in baseball? There's certainly a strong argument for it, to be sure. The pair have yet to allow a run in 18 1/3 combined

On Tuesday night, ESPN's David Schoenfield posited an interesting question on Twitter: Is the Tampa Bay relief combo of Jose Alvarado and Diego Castillo the best in baseball? There's certainly a strong argument for it, to be sure. The pair have yet to allow a run in 18 1/3 combined innings for baseball's best early season team, and each of them merited spots on our "2019 Breakout Players You Need to Know" list back in March. They're so good.

But are they the best?

We thought that was worth investigating, and we also thought it was worth doing one better, by trying to find which teams have the best relief trios in baseball. That is, if we set a minimum of 25 plate appearances per pitcher, which teams would have the best threesome of bullpen arms so far?

"Best," obviously, is a matter of opinion. For our purposes, we're going to use expected Weighted On-Base Average, which combines quality of contact (exit velocity and launch angle) and amount of contact (strikeouts and walks). We'll use that instead of actual outcomes because it's so early that poor defense or batted ball luck can have real impact right now, and we care more about what the pitcher can have more control over. (The Major League average for relievers is .321.)

We're not projecting forward. We're not saying these numbers will maintain, or that depth beyond three pitchers doesn't matter. We're saying so far, based on what we've seen, which trios have been the most dominant?

Don't worry, Rays. Making it "duos" would have only bumped you up to third. But there's still a lot of season to go.

1) Astros -- .176

Ryan Pressly, Roberto Osuna, Hector Rondon

You should hopefully, at this point, not be surprised by Pressly. We talked him up as a big trade piece to target when he was still with the Twins last July. We explained how he was using his high spin to dominate when he was with Houston last September. We named him as one of the "10 Best Relievers Right Now" in January. He's elite, even if he still feels anonymous. So far in 2019: He has nine strikeouts without a walk in 7 2/3 scoreless innings.

Osuna, for what it's worth, has yet to allow a walk or an extra-base hit, and Rondon has allowed only one walk, meaning that combined, this trio has a 25/1 K/BB ratio. Yes, that will help make them the best in the game.

2) A's -- .186

Blake Treinen, Lou Trivino, J.B. Wendelken

You saw Treinen's unbelievable 2018, and he's more or less following it up, having allowed just a single run. (While he does have a higher walk rate so far, as his 14.6 percent mark is more than double last year's, he's making up for it by cutting his hard-hit rate from 27.7 percent to 21.1 percent.)

You should probably know Trivino, who had a breakout 2018 and so far is backing it up with a 16/1 K/BB. But it's the well-traveled Wendelken -- included in 2013's Jake Peavy / Avisail Garcia trade and then in 2015's Brett Lawrie deal -- who may stand out, perhaps because he's currently got a 3.65 ERA.

Despite that, he's off to an impressive start, thanks to a 14/2 K/BB, and it's worth noting that in 16 2/3 late-season innings last year, he'd allowed just a single run. Combined, this trio has 41 whiffs, and just nine walks.

3) Dodgers -- .206

Kenley Jansen, Pedro Baez, Scott Alexander

This is a little surprising, right? Jansen's 2018 struggles with velocity and health were well-documented, Alexander's first season in Los Angeles was up-and-down, and Baez has spent most of the last half-decade being known better for his slow pace of pitching than for anything he's done production-wise. Plus, the Dodgers bullpen, with its 4.78 ERA -- largely thanks to the struggles of Joe Kelly and Yimi Garcia -- hasn't been great.

But for these three, at least, it's been "so far, so good." Jansen's cutter is down to a career-low 91.4 mph, yet he's whiffed a third of the hitters he's faced to go with a 2.16 ERA. Alexander has a 78 percent ground-ball rate, the second-highest in baseball, and a 1.23 ERA of his own. And Baez, as frustrating as he can be to watch, has cut his walk rate by more than half in the early going.

This feels like it can't last, and it very well may not. But this is at least what's happened so far, a surprising outcome for a questionable bullpen.

4) Rays -- .212

Jose Alvarado, Diego Castillo, Ryne Stanek

Now we're talking, and to be honest, let's call this a "tied for third," because there's not much meaning in a difference of .001 of expected wOBA here.

Alvarado has been unbelievable, and it's not just about the 99 mph pitch with wicked movement that tied up Charlie Blackmon and gained him national notice. He's struck out 13 without allowing an extra-base hit, along with an elite ground-ball rate. Castillo hasn't allowed an extra-base hit either; in fact, he has the best hard-hit rate in baseball, along with 10 whiffs of his own. We know it gets complicated with Stanek, who has started three times as an opener, but he has fewer innings thrown than Castillo.

He counts here -- and he's been strong with a 14/2 K/BB -- but this ranking wouldn't have changed much with Jalen Beeks or Adam Kolarek. Alvarado and Castillo are that good.

5) Padres -- .218

Kirby Yates, Craig Stammen, Robbie Erlin

What's fun about this trio is that they've all taken incredibly winding paths to get here. Yates is on his fourth team in six big league seasons. The 35-year-old Stammen didn't aven appear in the Majors in 2016, in between transitioning from Washington swingman to San Diego reliever. Erlin has been a starter with the Padres since 2013, but made only six appearances between 2015-17 due to arm injuries.

Yates picked up a splitter last year and has been dominant ever since; he has 17 strikeouts in 10 innings.

Kirby Yates is probably not someone you think about enough. He's been incredible this year. (17/3 K/BB, 0.90 in 10 innings.) pic.twitter.com/9pgukGeW2W — Mike Petriello (@mike_petriello) April 17, 2019

Stammen, quietly, has a 96/17 K/BB since the start of 2018, and has yet to walk a batter this season. Meanwhile, Erlin's 4.32 ERA is a bit misleading, because he also has an elite 99th percentile hard-hit avoidance rate, as well as more than one strikeout per inning.

The next five...

6) Cardinals -- .232

Jordan Hicks, John Gant, John Brebbia

7) Yankees -- .235

Aroldis Chapman, Adam Ottavino, Luis Cessa (who has outperformed Zack Britton and Chad Green)

8) Brewers -- .240

Josh Hader, Matt Albers, Junior Guerra

9) Red Sox -- .246

Matt Barnes, Brandon Workman, Hector Velazquez

10) Marlins -- .266

Tayron Guerrero, Sergio Romo, Nick Anderson

Bonus) Hey, where are the Giants?

This is a fair question, given that a fascinating collection of relievers does have baseball's lowest relief ERA. This is because of three things, really. First, Will Smith, who has been fantastic, hasn't reached the 25 plate appearances necessary to qualify. Second, this speaks to how their skill is reflected in depth, not just the top three. Third, while they have indeed been good, there's some evidence that the underlying performance hasn't quite lived up to the outcome numbers. Only two teams in baseball have overperformed their peripherals as much as the Giants. It doesn't mean they aren't good, because they are. It's just why they aren't here.