After a warm-up for the playoffs with Monday's pair of division tiebreakers, the postseason proper begins with the winner-take-all wild-card games: Colorado Rockies-Chicago Cubs on Tuesday at Wrigley Field; and Oakland Athletics-New York Yankees on Wednesday at Yankee Stadium.
Here are nine matchups to watch in the wild-card round:
Kyle Freeland vs. his abbreviated rest
The Rockies had the option of starting Antonio Senzatela on regular rest, but instead manager Bud Black will go with Freeland, who made his last start on Friday against the Nationals. Freeland has pitched on three days' rest once in the first two years of his big-league career -- but that was not in back-to-back starts. Rather, he pitched a third of an inning in relief on Sept. 27, 2017, and started on Oct. 1. But Freeland has earned this start with his exceptional second half of the season. Since the All-Star break, only three National League starters have a lower ERA -- Jacob deGrom, Aaron Nola and Jameson Taillon. By 2018 standards, Freeland is not a hard thrower, with an average fastball velocity that ranks 37th of 57 starters who qualified for the ERA title. He has generated exceptional production with his fastball, working with absolute precision, as detailed here.
But the question is whether any fatigue from working on a shortened schedule will affect that command. Freeland had a solid start at Wrigley Field earlier this season, allowing three runs in seven innings.
Jon Lester vs. the pitch count
The Cubs don't have Brandon Morrow. They don't have Pedro Strop. Carl Edwards Jr. has been struggling. Justin Wilson had a rough outing against the Brewers on Monday. Jesse Chavez threw two innings Monday. Randy Rosario and Brandon Kintzler both pitched against the Brewers too. A thin Chicago bullpen is compromised going into this game, and manager Joe Maddon could use every bit of help that Lester can muster.
Lester is 34 and one of the best postseason pitchers in baseball history; this will be his 26th appearance in the postseason and his third start in a winner-take-all game. He threw as many as 119 pitches in a game during the regular season, but mostly he worked 100 to 110, so the ability of the Rockies to push the pitch count to get him out of the game could be crucial.
Nolan Arenado vs. the adrenaline
Arenado's production makes him one of the best players in baseball, but his intensity is what makes him legendary: Coaches and players with other teams talk about how much they love to watch the Rockies third baseman play. But sometimes his effort seems to overwhelm his patience. The bigger the moment, it seems, the harder he tries, and that can work both ways. Arenado has been really good in recent days, with four homers in his past three games.
The hitters vs. the Wrigley Field conditions
As soon as Brewers manager Craig Counsell arrived at Wrigley Field on Monday, he descended about three dozen steps and made his way to the visitors dugout to glance at the flags above the field. If the wind is blowing in, driving the ball to right field or center field is a major challenge -- and in all but one game that Counsell participated in at Wrigley this year, he said, this was the way it was. Great pitching conditions. The forecast calls for temperatures of about 60 degrees Tuesday night, and Maddon, Black and just about everybody else in uniform will check the flags.
Gary Sanchez vs. any low pitch
The Yankees have stood by Sanchez this year through hitting slumps, questions about his effort and conditioning, and injuries. General manager Brian Cashman could not be more clear: He believes in Sanchez's talent and how he can be a pre-eminent offensive catcher. But despite missing weeks of the season with a groin strain, he had a staggering 18 passed balls -- by far the most in the big leagues. He has tended to drop strikes, he struggles to block balls in the dirt, and like a fielder with throwing yips, one mistake tends to lead to another. When Oakland has a runner at third base, the Athletics will be very aware of these problems.
The Yankees' hitters vs. Blake Treinen's stuff
A's manager Bob Melvin's dream scenario in this game would be to hand any kind of a lead over to his closer, who just completed one of the great relief seasons of all time -- a 0.78 ERA, seven earned runs in six months, 100 strikeouts in 80⅓ innings and just two homers allowed. Treinen has surrendered an earned run in one appearance since July 21. This year, opponents have swung at 42.8 percent of his pitches outside the strike zone, easily the highest percentage for any reliever in baseball; that's how good his stuff is. During the regular season, Treinen had nine outings of two innings and another of three innings, so if the Athletics have a lead in the seventh inning, Melvin could reach for the phone to deploy Treinen aggressively.
The Oakland youngsters vs. The Bronx Rumble
During last year's American League Championship Series, former Yankees Brian McCann and Carlos Beltran spoke with awe about how loud the Yankee Stadium crowds were, and of the intensity within the building, with each of them saying it was beyond anything they had experienced before. The Athletics have more veterans on their roster than people realize, from Jed Lowrie to Jonathan Lucroy to Fernando Rodney. But for some of their key guys, this will be a first test in the postseason, and they'll have to cope with what the Astros and Indians felt last year. In the first years of the new Yankee Stadium, the place sometimes seemed dead. But a new generation of fans seems inspired by Aaron Judge, Sanchez and the other young Yankees and has reached another level of volume.
The cannon of A's outfielder Ramon Laureano vs. Yankees third-base coach Phil Nevin
Laureano has played just 48 games in the big leagues, yet he already has established a throwing arm that might be the best in baseball. Incredibly, he racked up nine assists after becoming a regular in August, and sometimes it was as if opposing baserunners and coaches were either unaware of Laureano's unusual skill or wanted to test it themselves. Undoubtedly, the Yankees will discuss Laureano's arm in scouting meetings. The Yankees are not an especially fast team, and that could force Nevin to make really difficult choices about whether to send runners.
Aaron Boone vs. his bullpen choices
No team has a bullpen with better résumés than the Yankees. Aroldis Chapman, David Robertson, Dellin Betances, Zach Britton and Chad Green all have been among baseball's most dominant relievers in their respective careers. But there have been struggles along the way in 2018, especially with recent command: Robertson walked three in his past three outings; Betances walked a couple in an inning in Boston on Friday and issued 26 walks in 66⅔ innings this season; Britton walked three in an inning in his last appearance of the season and had 21 walks in 40⅔ innings. In a winner-take-all game, it'll be interesting to see how patient Boone is in allowing his veteran relievers to work through any command issues.