As close as the postseason race is in the National League, the Cy Young Award races in both leagues are turning out to be just as compelling.
With two weeks remaining in the regular season, baseball's best aces have just a handful of starts left to put their best foot forward and convince voters from the Baseball Writers' Association of America. The two races collide Sunday, when frontrunners Jacob deGrom and Chris Sale are scheduled to face off in Boston for one of the most high-profile pitching matchups of 2018.
Before these two aces (whose history goes way back) climb the hill at Fenway Park, here is a primer on everything you need to know about the Cy Young homestretch.
NATIONAL LEAGUE

Frontrunners
deGrom: 8-9, 1.71 ERA, 239 strikeouts
Max Scherzer: 17-7, 2.53 ERA, 277 strikeouts
Aaron Nola: 16-5, 2.42 ERA, 201 strikeouts
Scherzer's loss to the Braves Friday night marked one of the biggest sea changes in this year's Cy Young races, and not in the way that D.C.-area fans would like. Scherzer's ERA rose 21 points after he allowed a season-high six earned runs in Atlanta, meaning his 2.53 ERA is now third in the NL behind deGrom and Nola. Scherzer still has statistics in his corner, including the most wins (17) and strikeouts (277) on the Senior Circuit.
But at this point, deGrom's ERA advantage is truly hard to ignore. Not only would his current 1.71 mark represent the second-lowest ERA of this century behind Zack Greinke's 1.66 in 2015; it's well clear of the rest of the NL field. In fact, the last pitcher to finish at least 71 points ahead of the second-place finisher in his league in ERA was Pedro Martinez in 2000 -- one of the more celebrated pitching campaigns in history. Plus, deGrom already has history in the bag with his Major League record 26 consecutive starts with three runs allowed or fewer, which he'll look to continue Sunday.

With another solid start Sunday against a tough Red Sox lineup, deGrom could all but lock up his first Cy Young. That would make him the fourth Mets to take that award home after Tom Seaver (three times), Dwight Gooden and R.A. Dickey. deGrom would also own the fewest pitcher wins of any Cy Young-winning starter, thanks in large part to the lack of run support the Mets have put forth behind him. 
If voters need any further convincing, deGrom will likely have chances to make two more statements against potent offenses in the Nationals and the Braves. Scherzer would face the Mets on Thursday were he to start on normal rest, just missing deGrom's next scheduled start Friday, with at least one more start after that lined up against the Marlins. Nola's team appears to be the only one in this triumvirate with even an outside shot at the postseason, and so he'll figure to make each of his last three scheduled starts, first against the Mets and then possibly two matchups against the Braves.
AMERICAN LEAGUE

Frontrunners
Sale: 12-4, 1.96 ERA, 221 strikeouts
Blake Snell: 19-5, 2.03 ERA, 195 strikeouts
Trevor Bauer: 12-6, 2.22 ERA, 214 strikeouts
Corey Kluber: 18-7, 2.91 ERA, 194 strikeouts
Blake Treinen: 7-2, 0.85 ERA, 37 saves
Sale has been nearly untouchable on the mound, but the biggest question down the stretch is: Has he been on the mound often enough? The southpaw is expected to go three innings in Sunday's matchup against deGrom, which would get Sale back on to the qualified leaderboard with 150 innings (the standard is "one inning per team game"). Sale would still need 12 more innings after Sunday, assuming the Red Sox play all 162 games on their schedule, meaning manager Alex Cora would need to let him stretch out over his final two starts -- with Boston already well clear of the AL field. Teams in the Red Sox's current position typically give their players rest down the stretch, so what they do with Sale might be one of Boston's most compelling storylines before the postseason.

History shows that qualifying for the season-end leaderboard is crucial for a Cy Young candidate. While relievers have won the award a handful of times, no starting pitcher has claimed it without qualifying for the ERA leaderboard. Even if Sale were to finish with, say, 165 innings, it would mark the lowest total by any Cy Young-winning starter in a non-strike shortened season by a wide margin. 
Fewest innings pitched by a Cy Young Award-winning starting pitcher (non-strike season) 

1. 198 1/3 -- Clayton Kershaw (2014)
   
2. 200 2/3 -- Scherzer (2017)
   
3. 203 2/3 -- Kluber (2017)
   
   But Sale is certainly overdue, as 2018 will in all likelihood represent his sixth straight top-five finish in the Cy Young vote. Only three pitchers have previously compiled such streaks since the award was first given in 1956: Greg Maddux (1992-98), Roy Halladay (2006-11) and Kershaw (2011-17). Sale faces a less defined field than the NL, though Snell has closed the gap with his second-half surge. Tampa Bay's lefty has a good chance to finish with an ERA below 2.00, which would make him the first qualified AL pitcher to be able to say that since Martinez in 2000 (Sale could also earn that distinction with enough innings). Snell endured his own stint on the disabled list, but could have both wins and wins above replacement (WAR) on his side by season's end.
   Bauer took a major step forward this year, but, like Sale, will likely be docked for his time away from the field. Kluber might suffer more from not matching the incredible bar he set last season than anything else. Treinen must at least be considered for the Cy Young, considering how much trouble teams have had scoring off him. But after Zach Britton and his 0.54 ERA couldn't make inroads with voters three years ago, it's hard to see Treinen surpassing these supreme aces for the honors.