Bryce Harper was one of several Nationals who missed big chunks of the 2017 season because of injuries. But he’s back, just in time for the start of the playoffs. (Katherine Frey/The Washington Post)

Take a deep breath. It’s a nervous time of year.

The Washington Nationals begin their Major League Baseball (MLB) playoff season with a best-of-five-games series against the Chicago Cubs on Friday.

I go back and forth. Sometimes, I’m sure the Nats will beat the Cubs and go all the way to the World Series. Other times, I think they will lose their fourth playoff series in six years. Here are some reasons I’m sure the Nats will win.

Record vs. playoff teams: The playoffs are different. Only the best teams are still around. No more games against the Philadelphia Phillies or Cincinnati Reds.

Even though Washington had an easy schedule and won the National League East Division by 20 games, they also played well against playoff teams. The Nats had an excellent record of 17-12 (17 wins and 12 losses) against playoff teams.

Trea Turner also has recovered, which means the Nats once again have their starting lineup. That could be bad news for even the best opposing pitchers. (Toni L. Sandys/The Washington Post)

The Cubs weren’t so good. They were only 11-21 against playoff teams in 2017. Hopefully, the Cubs will keep losing against our playoff team — the Nats.

Starting pitching: No team in baseball can match the Nats’ two top starters: Max Scherzer and Stephen Strasburg. Washington has an unbelievable 86-31 record during the past two seasons in games when Scherzer or Strasburg started. That means the Nats win almost 75 percent of the games when Scherzer or Strasburg is on the mound. I like those numbers.

Healthy lineup: The Nats had lots of injuries this season. Bryce Harper, Trea Turner, Jayson Werth and Michael A. Taylor missed big chunks of the 2017 season.

All those players are back, and the Nats have their starting lineup for the first time in a long time. That means the Nats should be able to score runs even against some of the best pitchers in the National League.

But there are also reasons I’m nervous the Nats may lose to the Cubs and disappoint their fans again.

The Cubs: Chicago is no pushover. They won the World Series in 2016, breaking a 108-year streak in which the Cubs had not won one. These Cubs know how to win pressure-packed games.

Chicago is also red-hot. The Cubs have the most wins of any team in the National League since the all-star break, with a record of 49-25. (The Nats were 45-29).

Luck: A five-game series is usually close, and one play can make a big difference. A blooper may drop in, or someone may make an unbelievable play on a scorching line drive. Anything can happen, and that’s what makes playoff games fun but nerve-racking to watch.

The good news is that the first two games start early and are not on school nights (Friday and Saturday). So young Nats fans can stay up for all nine innings.

So watch. But take a deep breath.

Bowen writes the sports opinion column for KidsPost. He is the author of 22 sports books for kids, including nine baseball books.