So, Game 1 is in the books, and if any Angels fan says he or she isn’t deeply worried, they aren’t being truthful.

Unless they refuse to accept the reality of a concept often known as “momentum”.

Momentum is elusive; it comes and goes, ebbs and flows. But when a team has it, you can see it and that team can accomplish almost anything. Even if their players represent a franchise which did not play a postseason game for 29 years.

The Royals entered the American League Division Series with about as much momentum as is possible to have.

The Angels?

They entered the series without any momentum at all. Dead in the water, to be more precise.

They clinched the American League West on September 17 (15 days ago), and then finished their schedule by losing seven out of 10. They ended the season in Seattle, where they were swept, last weekend.

So, the Angels … best record in baseball.

So what? What have you done lately? Aside from lose a lot?

Meanwhile, the Royals twice made up big deficits to reach the playoffs, and nearly won the AL Central, and two days before tonight’s game they came from behind three times to defeat the Oakland Athletics in the wild-card game, overcoming deficits of 2-0, 5-2 and 8-7, winning 9-8 with two in the bottom of the 12th.

That game was so fraught, with so many unrealistic twists and turns, that nearly every reporter who saw it wrote of it in rapturous terms, especially Royals fan Rany Jazayerli, who works for Grantland.com.

So, the Royals have won eight of their past 10 … and they are doing it when it matters. With their season on the line.

They are the anti-Angels. A hit-and-run, small-ball, basepath-burning, ball-hawk defensive team that can create a run on a bloop, a steal, a bunt and a fly ball. They led the majors in steals and had the fewest strikeouts.

The Angels have turned into a ponderous, big-swinging team, the type that waits for a three-run home run and often gets it. They led the majors in scoring, and were among the leaders in homers, but they don’t run and they don’t play much defense.

Even Mike Trout, who is only 23, seems to have been sucked into this vortex of middle-age, big-biceps sluggishness. The guy who stole 49 bases two years ago, this year struck out 184 times — 48 more whiffs than the year before — and stole only 16 bases.

The Royals tonight did what they do. Their designated runner (Terrance Gore) stole a base and their defense was great, as it usually is, especially in the outfield, where the Angels saw four potential extra-base hits land in the gloves of Lorenzo Cain and Norichika Aoki.

The Angels’ two runs? Solo homers, of course. Sequential hitting, situational hitting … seemed like something of which the Angels are only dimly aware, and certainly not very good at.

It has been suggested in the NFL that a team (of late) has a better chance of winning the Super Bowl if it enters the playoffs on a roll, rather than as a team with the best record but an indifferent final month.

This is a baseball thing, too. Were the 2002 Angels the best team in baseball? They were pretty good, but what mattered was how well they played once they got into the playoffs.

Be afraid, Angels fans. Very afraid. Down 1-0 in a best-of-five series against a team that believes it is a team of destiny … and has been playing like it.

Not a good place to be.