Dustin Pedroia was one of a number of Red Sox defenders who flashed the leather in Wednesday’s opener, and defense played a key role in the 4-1 victory.

The Providence Journal / Gretchen Ertl

ANAHEIM, Calif. — Tonight is the Big Game.

You know it. The Red Sox know it. The Angels most definitely know it.

It’s always dangerous to say such things in the postseason. But after what we saw in Wednesday night’s series opener, who can argue?

The Red Sox are the defending World Series champions and, more important, they played like it in winning Game One. They did the things champions do while pinning a 4-1 defeat on the Angels, who had beaten them in eight of nine games during the regular season.

Clutch hitting — in particular, Jason Bay’s two-run homer with two out in the sixth inning that gave Boston a 2-1 lead.

A quality start from Jon Lester, who was pitching as well — no, even better — in his last inning than he was in the first.

A lights-out, three-strikeout performance from closer Jonathan Papelbon, who has yet to give up a run in 10 postseason appearances.

A couple of spectacular defensive plays in the eighth inning that preserved the one-run lead — Jacoby Ellsbury sprinting in to make a sliding grab of Mark Teixeira’s leadoff blooper in shallow center field, followed by Kevin Youkilis’ spot-on throw across the diamond from down the right-field line to Mike Lowell at third to nail Vladimir Guerrero and quelch a rally by the Angels.

So now they’ve won eight straight postseason games, going back to Game Five of the ALCS last year against the Indians. They have beaten assorted aggregations of Angels a total of 10 consecutive times in the playoffs — a streak that began with Dave Henderson’s home run heroics in Game Five of the ALCS in 1986. Tonight they turn to Daisuke Matsuzaka, he of the dazzling (if not exactly overpowering, considering the difficulty he has had going deep into games) 18-3 record, in hopes the Dice Man can keep them on a roll. He also has a streak of his own he’d like to extend: Dice-K is 9-0 on the road this season.

Imagine if the Angels lose tonight. They’d have to find a way to defeat Josh Beckett — which certainly is possible, considering that he’s been in questionable condition since straining his labrum last week — and then somehow beat Lester in Game Four in friendly Fenway . . . a task they weren’t up to in their own backyards Wednesday night. Then they’d have to come back here and beat Matsuzaka — or at least beat the Sox — again.

See why it seems that if Boston wins again tonight, the opening round of these 2008 playoffs will be all but over?

But it’s more than that. With Lowell and right fielder J.D. Drew hurting, and Beckett’s status somewhat in doubt, the feeling was that the Sox were vulnerable. In Game One, though, they looked invincible.

They played with an air of confidence. And so, now, there’s an air of desperation surrounding the Angels.

The Angels were the only team in Major League Baseball to win 100 games this season, but if they lose again tonight, they’ll be on the brink of seeing their championship hopes disappear into thin air.

That said, no one knows better than the Red Sox that, in the immortal words of the great Yogi of baseball, Lawrence Peter Berra: “It’s never over till it’s over.”

Boston won the World Series last year after falling behind Cleveland in the ALCS, three games to one. When the Sox won it all in 2004 for the first time in 86 years, they became the first team in major-league history to come back after losing the first three games of a best-of-seven series, as they did against the Yankees in the ALCS.

So there’s no way they’re going to take anything for granted, even if they do take Game Two tonight.

“We have to concentrate on what we have to do,” said catcher and team captain Jason Varitek. “Our hitters have to focus on having good at-bats. Our pitchers have to focus on making quality pitches. We all have to focus on playing good baseball.”

Just as they did in winning Game One, when they played like champions and gave their fans reason to believe that the World Series banner could continue to fly over Red Sox Nation.

jdonalds@projo.com