Last week, after Corey Kluber dominated the Mariners with an 85-pitch shutout, I rashly tweeted that Kluber is one of the best 10 starting pitchers in the game. That seemed to stir things up a bit on Twitter, and Giants fans were especially angered when I suggested Kluber is better than Madison Bumgarner. Kluber came back on Monday with another solid effort, allowing one run while striking out seven in 7.1 innings, improving his record to 12-6 with a 2.55 ERA.

But is he one of baseball's top 10 starters right now?

He's been very, very good. But is Corey Kluber one of the 10 best starters in baseball right now? Mark Cunningham/Getty Images

How do you even measure such a thing? We can take the easy way out and just look at wins above replacement for the season.

FanGraphs

1. Felix Hernandez: 5.8

2. Corey Kluber: 5.0

3. Jon Lester: 4.7

4. Clayton Kershaw: 4.5

5. Chris Sale: 4.2

Baseball-Reference

1. Felix Hernandez: 5.5

2. Clayton Kershaw: 5.2

3. Corey Kluber: 4.7

4. Johnny Cueto: 4.6

5. Chris Sale/Max Scherzer: 4.5

By WAR, Kluber isn't just a top-10 starter, but a top-five starter. Even ignoring how much you believe in WAR, the question is: Do you buy into Kluber's four-month streak as a true breakout performance? How much emphasis do we place on history? Zack Greinke won a Cy Young Award in 2009. Should that matter as to how we evaluate him now? Scherzer won the Cy Young Award last year when he was arguably the best pitcher in the American League. How much should that matter as to how we evaluate him in August 2014?

Bill James actually devised a method to answer this question a couple of years ago. He wrote:

Everybody starts out with a ranking of 300.0, and you can’t go lower than 300, even if you pitch badly. If you’re at 300, you’re unranked; you’re only actually on the list if you have a current score higher than 300. There would typically be 150 to 180 pitchers who are, at the moment, ranked. Pitchers never actually pitch badly enough that they would rank below 300 (if it were possible to do so) for more than two or three starts, because if you pitch that badly, you lose your position in the rotation. When a pitcher makes a start, we: a) Mark down his previous ranking by 3%, and b) Add 30% of his Game Score for the start. We base the rankings on Game Scores, which means that we ignore wins and losses, but give weight to innings pitched, runs allowed, earned runs allowed, walks and strikeouts.

James also adjusted for park effects, inactivity (if a pitcher doesn't pitch, his overall rating goes down) and postseason play, which he factored in. Anyway, his site unfortunately doesn't update the rankings, so I don't know how Kluber would rank. So I'll just wing my own top 10.

1. Clayton Kershaw

The best pitcher in baseball, and I don't think anybody is really arguing this. Hernandez ranks higher on the WAR lists because Kershaw missed April, so he doesn't have as many innings.

2. Felix Hernandez

3. Adam Wainwright

Similar in many ways -- veteran right-handers (it seems weird to call Felix a "veteran," but he has been around a long time) having their best seasons.

4. Chris Sale

He's 10-1 with a 2.09 ERA with 129 strikeouts and 20 walks in 116 innings. Incredible numbers. He has cut his home run rate from last year, even though he pitches in a good home run park. I'm not knocking Wainwright when I say this: Sale is better. But he did miss time earlier this year and I think we have to give Wainwright extra credit for his durability.

5. Yu Darvish

6. David Price

I'm not completely comfortable ranking Price this high -- he's ninth in FanGraphs WAR and 25th in B-R WAR. He has 189 strikeouts and just 23 walks but has allowed 20 home runs, and he goes from a good pitcher's park with a good Rays defense behind him to a better hitter's park with a below-average Tigers defense behind him. It's possible that change will reveal that he did benefit from pitching in Tampa. Or it may not reveal anything. But Price has been good a pitcher for five years, and his new approach of pounding the strike zone has basically turned him into a harder-throwing version of Cliff Lee.

OK, now things get a little murky. Let's start with Kluber versus Bumgarner, because that got a lot of feedback on Twitter.

I know Bumgarner has been a solid pitcher for several years. He has come up big in the postseason. But in comparing 2014: Kluber has the better ERA, the better FIP, the better strikeout rate, a lower walk rate, a lower home run rate, a higher ground ball rate, the lower batting average and OPS allowed, has pitched more innings and has done it in a DH league while pitching in a tougher park with a lousy defense behind him. I can't rate Bumgarner ahead of Kluber.

(By the way, Bumgarner's career high bWAR is 3.8, achieved last year. A lot of that is park effects. Giants fans will point out that Bumgarner has a better ERA on the road in his career than at home, but that's not the way park effects work. Bumgarner still has the advantage of pitching half his games in a pitcher's park.)

Jon Lester? Hmm. Lester is a No. 2 starter having a No. 1-level season. But he had a 3.75 ERA last year and 4.82 the year before. FanGraphs and B-R differ on his value -- FanGraphs ranks him third overall while B-R ranks him 22nd. Kluber, by the way, had a 3.85 ERA last year with excellent peripherals. If you give Lester a little extra credit for his postseason last year, I'll reluctantly give him the nod, although I think his track record works against him just as much as Kluber's lack of track record works against him.

Scherzer is similar to Lester, except his No. 1 season came last year. He's been nearly as good this year, even though his BABIP has once again bounced up:

2011: .314

2012: .333

2013: .259

2014: .316

One reason Scherzer's BABIP is usually high is that he does pitch up in the strike zone, unlike a lot of pitchers who pound the zone at the knees. Of course, the other reason is the lousy Tigers defense. (Take note, Mr. Price.)

Johnny Cueto? I'm not quite sure what to do with Cueto, giving his history of injuries. But we're talking best starters right now, and Cueto has been healthy and effective all season and he has always been effective even when he has missed time.

Garrett Richards is another young starter having a breakout season. While Kluber relies on command and a wipeout curve, Richards has upper 90s heat and a deadly slider. Their numbers:

Kluber: 2.55 ERA, .233/.277/.341, 26.7 percent K rate

Richards: 2.58 ERA, .195/.267/.259, 24.7 percent K rate

Kluber rates a little higher in WAR because he has pitched 12 more innings and Richards benefits from a pitcher's park. Tough call here. Like Kluber, Richards doesn't have much of a track record before this season. There's no denying his stuff. Richards has the fourth-lowest BABIP allowed among starters at .258 (Kluber's is .309) and a low rate of home runs per fly ball (third-lowest among starters). I think those numbers indicate Richards has pitched in more good luck than Kluber this season. But I could be wrong; his stuff is nasty.

OK, where does that leave us? With apologies to Zack Greinke, Cole Hamels, Hisashi Iwakuma, the injured Masahiro Tanaka and maybe a couple of others, the top 10 starters in the majors RIGHT NOW:

1. Kershaw

2. Hernandez

3. Wainwright

4. Sale

5. Darvish

6. Price

7. Cueto

8. Lester

9. Kluber

10. Scherzer

Including Richards, you could rank the final four guys in any order, really. If you want a longer track record, go with Lester and Scherzer. If you like raw, unhittable stuff, go with Richards. If you think postseason history matters, go with Lester. If you like 28-year-olds out of nowhere with curveballs that make major league hitters weep in frustration, go with our man Corey Kluber -- one of the 10 best starters in the game.