MLB playoffs: The under-the-radar stat that could swing Red Sox vs. Astros and Dodgers vs. Brewers

We pointed out one under-the-radar thing to watch for each of the Division Series, something that might not jump out in the team or individual stats, but would be fun to watch. And they proved to be important pieces of each matchup. 

Now it's time to do the same for the Championship Series in each league.

ALCS: Astros vs. Red Sox

The Red Sox and Astros were the two best teams in the league all year, so let's not waste time talking about their Cy Young candidates (Chris Sale and Justin Verlander), their MVP candidates (Mookie Betts and Alex Bregman), or their high-powered offenses and power pitching staffs.

Something that might prove to be a difference maker is the Red Sox's running game. They were third in the majors in stolen bases this season, and one of only two teams with a success rate better than 80 percent (Angels). And just looking at the Astros from a team level for the entire season won't tell the story of their ability to control the running game.

They were middle of the pack during the regular season in throwing out would-be basestealers, but they acquired Martin Maldonado at the deadline in July, and he'll have a major impact on that. Before that trade, the Astros' catching duties were split between Brian McCann and Max Stassi, neither of whom threw out 25 percent of runners attempting to steal (the MLB average was 28 percent).

So will the Red Sox take advantage of McCann when he's behind the plate? Or can they steal a base in a big spot against Maldonado, who was second in the majors this year by throwing out more than 45 percent of runners attempting to steal?

Despite McCann's history, he's not the slugger he once was (career-low .339 slugging percentage this season), so he and Maldonado will play based on matchups, and the right-handed hitting Maldonado will likely get more chances with the Red Sox likely to start a lefty in four of the seven matchups.

Which means that Maldonado will likely be behind the plate when Justin Verlander and Gerrit Cole are pitching for the Astros -- runners were successful on 14 of 19 attempts with Cole on the mound, but opponents were only 3 for 7 all season against Verlander. And in 315 innings behind the plate since joining the Astros, Maldonado has thrown out five of eight.

NLCS: Dodgers vs. Brewers

The Dodgers hit eight home runs in their four-game Division Series win over the Braves, and Brewers pitchers didn't allow a home run in their sweep of the Rockies. So this series (like most of baseball these days) could come down to the long ball. But where will that show up most?

As mentioned in the NLDS preview, the Dodgers get most of their power from the left side. They had the highest home run rate and the second-highest slugging percentage in the majors from left-handed batters during the regular season (the Brewers were second and first, respectively), and four of their eight NLDS home runs came from left-handed hitters.

Clearly the Brewers will need to neutralize those hitters when they consider matchups. They only used two left-handed pitchers in the series against the Rockies -- Game 3 starter Wade Miley, and relief ace Josh Hader. But they're starting Gio Gonzalez tonight, a guy who's faced 139 left-handed batters this season and allowed two home runs.

Hader is the key though. He led the majors in relief outings of more than an inning pitched, and the Brewers will deploy him early and often in this series. So if the left-handed reliever can handle the lefties, then all should be good, right?

Not so fast. The Dodgers still have dangerous righties; their two best hitters, Manny Machado and Justin Turner, are right-handed and their cleanup hitter is a switch-hitter (Yasmani Grandal) who would face Hader from the right side. And if the Dodgers alternate righties and lefties like they did in Game 4 on Monday, then Hader will have to face a few of them if Craig Counsell wants to get multiple innings out of him.

Hader was susceptible to right-handed hitters this season. He's faced 106 left-handed batters this year and allowed one home run, but he's allowed eight homers to righties, and they've had a huge impact on the game. Now Hader is usually pitching in big spots, but of the eight longballs he allowed to right-handed hitters, three gave the opponent the lead, three more tied the game, and the other two cut the Brewers' lead to one.

Here are Hader's splits this season:

We know Hader will be deployed in big spots in this series, but he's going to have to get through the Dodgers' righty sluggers to give the Brewers a chance to get to the World Series.