What to expect out of Washington Nationals’ starters Gio Gonzalez and Tanner Roark in 2018...

With just a few weeks left until Spring Training, only one team in Major League Baseball employs at least four starting pitchers who’ve finished among the top 10 in Cy Young voting over the past two years: the Washington Nationals.

Three-time winner Max Scherzer and former No. 1 overall pick Stephen Strasburg garner the most attention — and deservedly so — but Gio Gonzalez and Tanner Roark have each put together a Cy Young-caliber season between the last two years.

“We’re really satisfied with what we’ve got; we’ve got ourselves a good rotation,” GM Mike Rizzo said on MLB Network Radio last Wednesday. “We’ve got four horses at the top. We’ve got a Cy Young winner [Scherzer]. We’ve got [Strasburg], who should win one and may win one, and Gio Gonzalez, and Tanner Roark. We’re solid four.”

Gonzalez is fresh of a career year, finishing the 2017 campaign with a 15-9 record, 2.96 ERA, 1.18 WHIP, 188 strikeouts and 79 walks in 32 starts and 201 innings. The 32-year-old lefty put together a 6.6 bWAR season — the third highest mark in the majors among pitchers.

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While his peripherals are impressive, the deeper numbers suggest Gonzalez is due for some regression in 2018. His 3.93 FIP was Gonzalez’s highest mark ever for a full season, as was his astronomical 81.6 percent left-on-base percentage.

The biggest concern for Gonzalez is the steady decline of his fastball velocity since 2012. Hitters have teed off on his fourseamer and sinker over the last two seasons, prompting him to significantly bump up his curveball and changeup usage in 2017.

The immediate results looked good on paper, but his reliability will only waver as his velocity continues to spiral.

“He can’t rely on a 95-96 mph fastball from the left side like he used to,” Rizzo said on 106.7 The Fan in late June. “Now he’s 89-92, he pitches low in the zone, he’s gone back to relying on that nasty curveball that he has, and really has developed a third pitch in the change, so pitching more, throwing more strikes, challenging hitters and getting ahead of them. I think that’s always been the key to him and I think that he’s really now beginning to become more of a pitcher than he was when he was young and had that electric arm.”

Roark had an up-and-down season last year, posting a 13-11 record with a 4.67 ERA, 1.34 WHIP, 166 strikeouts and 64 walks in 32 appearances (30 starts) and 181.1 innings. While he’s only two years removed from a 5.5 bWAR campaign, Roark took a troubling step in the wrong direction last season.

The good news for Roark is that his troubles with the long ball are likely to diminish.

Roark allowed a home run on 13.5 percent of fly balls last season, four percent above league average. For reference, FanGraphs categorizes any HR/FB rate above 13 percent as “Awful.” This suggests Roark’s ERA was inflated and will likely regress in 2018.

Even amid a down year, Roark was still among the best groundball pitchers in the game. His batting average allowed on balls in play was exactly league average (.300), but he also stranded runners at an unsustainably low rate (66.3 percent).

“Tanner is the most under-appreciated player we’ve got,” Rizzo told reporters at NatsFest in December. “He’s the ultimate team player. This guy never says a negative word. He’s all about the team. He’s the type of guy that I love having him on the mound, you know he’s going to leave everything out there, and he’s been very, very successful in his career here, and we hope that continues. We control him for a long time, and we’re looking forward to him having a big season.”

Despite the fact that Gonzalez had one of the best years of his career in 2017 while Roark endured one of his worst, the pitchers are trending in opposite directions. Gonzalez certainly has better strikeouts numbers and a more established resume, but Roark is the safer bet to perform in 2018.