The Boston Red Sox have made it a habit of trotting out no-hitters in recent years: Four out of the last six no-no's in the American League have come from Boston hurlers, including this week's gem from Jon Lester.

There've been 211 no-hitters since 1900, but what's unique about Lester's is that we have a data-driven grade for it. Over the last couple of years, Minneapolis-based scouting firm Inside Edge has been introducing player report cards which rate hitters and pitchers on a variety of metrics and then spitting out a grade. Unlike the also new Pitch f/x system which uses cameras placed all around stadiums to track pitches, Inside Edge has scouts -- former major leaguers -- identifying pitches and their outcomes.

So what did Lester get? An A-, which prompted anonymous blogger Abu Muqawama to protest:

...there is something wrong when a guy throws a freaking no-hitter and grades out at A-. A minus?!

But according to other Inside Edge scores, Lester's game may not even have been the best so far this young season.

"It is really difficult to score an A+ on those report cards on a single game," Kenny Kendrena, product and marketing director at Inside Edge, told me. "We're really breaking down these outing in so many different ways that you really have to be almost perfect to get an A+."

Pitchers are graded on eight broad categories and 24 subcategories. For example, the Dominance category is determined by a pitcher's performance in three subcategories: Percent of outs that are strike-outs in four pitches or less, percent of 1-2-3 innings, and percent of swing-and-miss strikes.

According to Lester's report card, the southpaw excelled in finishing off hitters, throwing off-speed pitches, and his overall effectiveness and dominance. Where he came up short was with his command and efficiency. 55 percent of his off-speed pitches were strikes, below the major league average of 61 percent, earning him a D+ in that category.

Lester also got F's for his inability to work through hitters quickly. According to Inside Edge, a batter was at the plate for more than four pitches 41 percent of the time, markedly below the league average of 65 percent. Although not factored into Inside Edge's grade, Lester's 130 pitches were the most thrown by a starter this season. Viewed through the lens of the report, it looks like Lester's stuff wasn't really fooling Kansas City Royals hitters. (Or as my fellow Portfolio.com staffer Taylor Umlauf put it, "sounds more like the Royals hitters were hung over rather than Lester being dominant.")

Who does get A+'s? Inside Edge's search system isn't quite there yet (in order to find past results, Kendrena had to go through each report), so I wasn't able to get any pitchers who posted an A+ this season. But here are some pitchers who managed to get mere A's:

May 15, Cole Hamels, Phillies shutout Braves
May 5, Ervin Santana, Angels shutout Royals
May 2, Tim Hudson, Braves shutout Reds
April 19, Andrew Sonnanstine, Rays shutout White Sox

There is the argument to be made that errors are introduced when humans are responsible for keeping track of outcomes -- you only have to watch one or two ball games to see a couple of bad calls from umpires. But this comment from Red Sox catcher Jason Varitek -- who amazingly has caught all four recent Red Sox no-hitters -- hints that Lester wasn't wowing everyone:

"This was a weird one," Varitek said. "I didn't really know he had a no-hitter until the eighth. I looked up in the seventh and saw that he was around 100 pitches and he did his job. I glanced in the bullpen and saw nobody warming up and thought that was weird."