Five key story lines as the 111th World Series gets underway Tuesday in Kansas City.

1. Fastballs. The Mets love throwing them. The Royals love hitting them.

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During the regular season, the Royals were second to only the Blue Jays among major-league teams in their ability to hit fastballs, according to FanGraphs.com.

The Mets, meanwhile, were the most effective staff in the majors when throwing fastballs, per the same metrics. (After a dominant National League Championship Series in which New York never trailed, the Chicago Cubs' hitters can verify as much.)

So we're about to find out which team is better at hardball. The Royals' hitters could have an edge -- at least early in the series -- because they'll be in a better rhythm thanks to the shorter layoff before the World Series. Speaking of which . . .

2. The NLCS sweep is a bad sign for the Mets.

In the postseason, at least, there is such a thing as winning too quickly.

This is the seventh time the World Series has paired one team that swept its LCS against another that played at least six games, according to STATS LLC. In the six prior instances, the team with the shorter playoff went 5-1.

Moreover, eight of the past nine World Series have been won by the team with the shorter playoff; the 2009 Philadelphia Phillies were the lone exception.

The Mets will have had five open days between Game 4 of the NLCS and Game 1 of the World Series. Will Daniel Murphy dig into the batter's box and extend his record-setting streak of six consecutive postseason games with a home run? It won't be easy, particularly with Royals pitching coach Dave Eiland telling our Ken Rosenthal, "He's very comfortable right now. I'll leave it at that."

3. The National League rules will be problematic for the Royals.
You wouldn't think that because the Royals' athleticism recalls the traditional NL style, but they rely heavily on the production of designated hitter Kendrys Morales.

Morales led the Royals with 106 RBI during the regular season and was arguably their most consistent hitter during the AL playoffs, with a .872 OPS and four home runs over 45 plate appearances.

Morales is more important to the 2015 Royals than his predecessor, Billy Butler, was in 2014. And if the Royals' performance in New York reflects that, they won't be the first AL champion to experience a letdown in the NL ballpark: Since 2006, American League teams are only 8-17 while playing under NL rules during the World Series.

4. Is Yoenis Cespedes healthy? No matter what the Mets say publicly, we won't know for sure until we see him take strong, healthy swings in Game 1. His left shoulder injury -- of uncertain origin -- was serious enough that he left the NL pennant clincher early and received a cortisone injection. That's very worrisome given the strong disincentive to acknowledge any injury so close to his entering free agency.

5 Home and road trends. The Mets went 4-1 on the road in the NL playoffs and notably scored the first run in each of those games. But now they're encountering the Royals, who are 5-1 at Kauffman Stadium in the postseason and had the AL's third-best home record during the regular season (51-30).