The early summer months have seen a host of fantasy-viable starter callups, signaling a rush to the waiver wire for fantasy owners struggling to keep their heads above water in the increasingly dire pitching landscape. Many of the fresh new faces featured here have made impressive strides in the early goings, flashing impressive results and tempting velocity trends. But which burgeoning hurlers figure to have sustained fantasy relevance once regression kicks in? Let’s dig into the numbers and find out.

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Jacob Faria (SP – TB)
The toast of the call-up class thus far, Tampa Bay righty Jacob Faria has gone from speculative flyer to standard-league mainstay in just five starts, boasting a 2.23 ERA over his first 32-plus MLB innings, certified by a 2.84 FIP that is a top-five mark among qualified starters over the last month.

The sample is certainly small, but Faria looks the part of an overpowering stud, coaxing above-average chase rates and swinging strike rates while flashing a truly elite changeup that has earned a 47.6% strikeout-minus-walk (K-BB) rate while surrendering a -17 wRC+ on 72 offerings.

Encouraging signs abound for Faria, though there is reason to practice temperance before penciling him in as an elite ERA contributor for the long haul. The 23-year-old righty hasn’t been throwing either his four-seam or his slider for above-average strikes, despite the strong results on both pitches. That slider’s combination of a .240 ISO allowed and a .050 BABIP also seems puzzling, and with a K-BB under 8% on that pitch, we might expect some poorer results to come.

Even so, it’s not exactly a scoop to suggest that Faria won’t continue to pitch as if he were competing for the ERA title. Expect closer to a low-3.00 ERA going forward and you won’t be disappointed.

Sean Newcomb (SP – ATL)
It appears that regression has already come calling for Sean Newcomb. as the Braves southpaw took a whooping from the mighty Astros last night, surrendering 10 hits and seven earned runs while raising his season ERA from a pristine 1.48 to a more sensible 3.58.

And with two walks over 3.1 innings, Newcomb’s BB/9 jumped to 3.25, a bit more in line with the bloated minor-league walk numbers that made Newcomb such a touch-and-go fantasy prospect when he premiered last month. The granular numbers suggest that it could have been even worse for Newcomb, who threw under 33% of his pitches in the zone and managed a mere 50% first-pitch strike rate during the start.

The good news is that most shrewd standard-leaguer aren’t likely smarting from Newcomb’s meltdown, with his current two-start week against the Astros and Nationals marking a clear-cut stay away. This should give us an indication of where Newcomb stands in the fantasy landscape, despite his impressive early run. He’s a promising talent, but for standard leagues, he’s a match-up play for now.

Francis Martes (SP/RP – HOU)
Luis Castillo (SP – CIN)
Grouping Francis Martes and Luis Castillo together seems intuitive because they represent very similar profiles; untested, hard-throwing youngsters who ooze both intriguing bulk-strikeout upside and major command-issue downside.

Granted, neither the Houston up-and-comer Martes nor the Cincinnati flamethrower Castillo have logged more than a handful of MLB innings this season, but even in the small sample, the high highs and low lows are on full display. Velocity hawks will undoubtedly salivate at the triple-digit readings from Castillo and the not-too-shabby 98 mph showings from Martes. Still, for both of these guys, the fastball actually seems like a liability, with Martes and Castillo each flashing 200+ wRC+ results on that pitch over 200 or so offerings, thanks largely to their inability to throw the heater consistently for strikes. (The K-BB on Marte’s four-seam is -5%, for goodness sake.)

The meager chase rates and relatively mortal swinging-strike numbers on the fastballs for both Martes and Castillo only serve to confirm that what fantasy owners are rostering here are blind gambles on upside. Granted, in the current pitching environment, low-cost/high-upside fliers are hard to come by. Still, neither of these players appear poised for major ERA or WHIP regression. If I were rostering either, I’d try to trade them away for a less volatile asset after the next double-digit strikeout game.

Dinelson Lamet (SP/RP – SD)
San Diego’s hard-throwing Dinelson Lamet might have lost the faith of fantasy owners when he coughed up seven earned runs in consecutive starts to begin June, a rough stretch that explains why his season-long ERA stands at an unappetizing 5.35. The same small-sample illusion underlines for his less-than-stellar walk rate of 2.68 BB/9, unnaturally bloated thanks to a five-walk outing against Arizona on June 6th. Lamet has surrendered a total of six free passes across his other six starts.

Meanwhile, Lamet’s 12.2 K/9 is the stuff of fantasy stardom, buoyed by a 49% reach rate and 24% swinging-strike rate on his electric slider. The young hurler does appear to be searching for a strong third pitch to pair with that daunting slider and his high-90s fourseam. Thus far, Lamet’s changeup hasn’t been cutting it results-wise (194 wRC+ on 64 pitches), but the .556 BABIP on that pitch should signal that some positive regression is looming, as should his suspiciously low 57% strand rate overall.

The undrafted Dominican import might not have the prospect pedigree of some of the other young arms featured here, but he’s got strikeout upside to burn without the alarming control issues of Castillo and Martes. There’s a chance that he’s the most addable name of this group after Faria.

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Tom Whalen is a featured writer at FantasyPros. For more from Tom, check out his archive or follow him @tomcwhalen.