We're coming up on the end of April, which is a magical time in every MLB season. There are hot starts, and there are hot starts, and we're nearing the time when it becomes acceptable to point to a body of work in the current season as something more than a two-week blip. Consider, for instance, the top eight qualified ERA leaders in Major League Baseball going into Thursday's action: Mark Buehrle (0.64), Aaron Harang (0.85), Ervin Santana (0.86), Alfredo Simon (1.30), Johnny Cueto (1.38), Jesse Chavez (1.38), Martin Perez (1.42) and Yovani Gallardo (1.42). Aside from Cueto, this is a laundry list of people you don't expect to see leading the league in ERA -- and you can probably figure out without any special assistance which names likely won't be on the list come the All-Star break.

The tricky thing is to separate the meaningfully surprising performances from the ones that are expected, such as Cueto; sample-size mirages like Buehrle; or straight-up black-magic wonder tours like Aaron Harang, whose current season line is the most bizarre this side of Aaron Cook's 2012 stint in Boston. (Seriously, Harang is somehow stranding over 90 percent of runners on base while about 70 percent of his balls in play are either fly balls or line drives. It's nuts.)

It'll be awhile before we can say anything definitive about whether a particular pitcher's season is a breakout or a mirage -- in some cases, we may need to wait until the end of 2015 to truly evaluate how closely this season's pitching performances matched up to true talent level. But we can at least identify a couple of guys to watch outside of the by-the-numbers ERA leaders thus far.

Jenrry Mejia, New York Mets

Even without the arm of staff ace Matt Harvey, the New York Mets quietly had a rotation whose upside ranged from above average to very good. Bartolo Colon, Zack Wheeler and Jon Niese seemed to be underrated over the offseason for a variety of different reasons. While those three pitchers have been mixed bags in terms of early results -- and while a lot of the Mets rotational upside chat relies on Noah Syndergaard popping onto the 25-man roster sometime in the middle of the season -- the Mets have gotten a significant lift from starter-turned-reliever-turned-starter-turned-reliever Jenrry Mejia. Since joining last July, Mejia has a 2.16 ERA -- but prior to that, he was mainly notable for how poorly the previous Mets administration mishandled his development back in 2010. (Mejia was supposed to be one of the second-tier pitching prospects from slightly before the time when Harvey, Wheeler and Jeurys Familia were the big three in the Mets farm system. His career was partially derailed by Tommy John surgery, but now he's fully recovered and showing signs that he'll make good on the promise that convinced the Mets to call him up -- at 20 years old -- in the first place.)

Mejia's cutter and curveball both look like plus pitches in his most recent stint in the majors. The big question is how well he can command his pitches. So far he's already walked 14 batters against 25 strikeouts in 22.2 IP this season, which is many more walks per inning than he wants to be surrendering. If Mejia's start proves to be a fluke, it'll likely be because he's unable to get his pitches under control -- but from what he's shown so far, he's put together the talent to succeed at the major league level.

Yovani Gallardo, Milwaukee Brewers

Gallardo makes the tail end of that list of ERA leaders -- and it's about time, as far as Brewers fans are concerned. Gallardo is a guy who has never quite lived up to his potential. He's been solidly above average most of his career, but he was supposed to be the ace of the Milwaukee rotation when he came up. (Functionally, he's been that team's ace for the past five years or so.) The main concern with Gallardo was last season's line -- 180.2 IP of 4.18 ERA baseball at 27 years old. That's a significant step back from Gallardo's career numbers. The fear about guys whose control never really develops -- Gallardo has a career 3.4 walk rate, which is on the high side -- is that as soon as the stuff tails off, the pitcher is just done.

The stuff appears to still be there for Gallardo, and he's only walking 2.6 batters per nine at the moment. While we're a bit too far down the line in Gallardo's career to feel comfortable theorizing that he's just fixed his command, at least for now he seems to have bounced back from being a sub-league-average starter last season.

Edinson Volquez, Pittsburgh Pirates

Stop me if you've heard this one before: A pitcher with good stuff but long-standing control issues has resurfaced on the Pittsburgh Pirates and is suddenly mowing down major league hitters. For the time being, at least, Edinson Volquez is this season's Francisco Liriano. (The actual Liriano, it may be worth noting, has an ERA of 4.22, which is more or less right back in line with his career numbers.) The Pirates do have some sort of recent track record at rehabilitating this kind of pitcher -- though it should be mentioned that, even though just about every pitcher in the Pirates organization had a career year in 2013, it didn't stop guys like Jonathan Sanchez from washing out. But generally speaking, Volquez has had many recent big-league stints end the way most fireworks do. He should be difficult to fully trust until the season is over and in the books and he's asking for $100 million in free agency. Something interesting about Volquez (18th on the ERA leaderboard among qualified players) is that his strand rate is a fairly pedestrian 78.1 percent, as opposed to strand rates in the high 80s and low 90s for virtually ever pitcher above him.

Martin Perez, Texas Rangers

The most important thing about Martin Perez's game right now is that he's a Rangers pitcher getting over 60 percent of his balls in play on the ground. Given the rather unforgiving confines of the ballpark in Arlington for pitchers, it's far better to be hanging out near the two-thirds mark than to be near last season's 48.1 percent. Perez isn't the kind of pitcher that can sustain a 1.42 ERA across an entire season -- he's not an especially proficient strikeout pitcher and has a middle-rotation ceiling at best -- but given the other guys in the Rangers rotation, he doesn't have to. He's been invaluable so far in keeping the Rangers from embarrassing themselves in the first month of the season while they deal with a myriad of starting-rotation woes.

This appears to be a legitimate change in approach. Almost 40 percent of the pitches that have come out of Perez's hand so far this April have been sinkers, and he's drastically cut back the amount he uses his four-seamer and change-up combo so far. It'll be interesting to see how teams adjust to what he's doing with it.

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There are other pitchers for whom similarly convincing arguments can be made -- for instance, Michael Pineda -- but for now, these are four of the guys who've looked particularly promising for reasons besides the Random Number Generator writ large that is the first month of the season.