The right-hander did his job beautifully, silencing the Royals for eight dominant innings. The newly designed offense caught fire after idling for seven innings, stringing together five consecutive hits in a five-run eighth inning for a 5-0 decision.
Weaver held the Royals to four hits and walked none while striking out 10 in eight innings. He's the third Angels pitcher to notch double-figure strikeouts in an opener, joining Nolan Ryan -- the Express did it in 1973 and '75 -- and Andy Messersmith (1970).
Scott Downs delivered the final three outs after the ace had done the heavy lifting.
Now it's Haren's turn to show his stuff in a Saturday matinee against a Royals outfit that can bring some thunder of its own.
Weaver muffled Kansas City by controlling the top of the order, holding Alex Gordon, Lorenzo Cain, Eric Hosmer and Billy Buter hitless in 11 at-bats with eight strikeouts. Gordon and Cain each went down three times.
"The bottom line is we knew what he had," Butler said. "I've faced him before, and he was locating his pitches well and was executing. We had some opportunities, but he pitched a good game. You can't take anything away from him."
Weaver led the Majors with 233 strikeouts in 2010, settling for 198 last season by getting more early-count outs.
"I don't think you put pressure on a guy to do it every night," Angels manager Mike Scioscia said. "He pitched to his capabilities tonight."
Weaver, who had four complete games last year while reaching a career-high 18 wins, would have loved the opportunity to finish it. But Scioscia decided it was no time to force the issue after the Angels hammered the Royals' bullpen with four consecutive singles, Erick Aybar's bases-clearing triple and Torii Hunter's RBI single.
"He wanted to [continue], but he knows, understands what our feelings are, what our thought process is," Scioscia said. "He wanted to pitch deep enough in the game to win. There might have been merit to give him an extra 10 to 12 pitches if we needed it."
So there it is, the only way Haren can top Weaver: a complete-game shutout.
"I guess it's just the competitive side of me," Weaver said. "I want to pitch until the wheels fall off. The guys came up with five runs and Scioscia put the kibosh on it. My competitive nature is I never want to come out of a game."
Finishing second in the American League Cy Young Award balloting to Justin Verlander, Weaver established a career high in innings (235 2/3) as well as wins and earned run average (2.41).
At 29, the cross-firing pride of Simi Valley, Calif., is clearly at the top of his game.
"That's no fluke," Royals manager Ned Yost said, assessing Weaver's performance. "That's what we see from Weaver every time we face him."
Pujols, 0-for-3 with a lineout and an intentional walk, brought a hitter's perspective from St. Louis to assessing his new teammate.
"The way [Weaver] hides the ball, it's amazing," Pujols said. "It's tough. It's almost like the resin bag is coming off his hand, the way he keeps you off balance. Cutter, sinker, good changeup. The changeup is his best pitch. He had it all working for him tonight."
This was Weaver's first meaningful test with new catcher Chris Iannetta, acquired from the Rockies over the winter in exchange for pitcher Tyler Chatwood.
Iannetta and Weaver were in tune, harmonizing with a nice tempo.
A former Long Beach State teammate, Rockies star Troy Tulowitzki, had given Weaver an advance scouting report on the receiver who would replace Jeff Mathis.
"I knew when Chris came over he was a heckuva defensive catcher," Weaver said. "I talked to Tulowitzki about him. He [Iannetta] is a rock back there."
Scioscia can talk about the pitcher-catcher relationship as the game's most important element until he's a Dodger shade of blue in the face.
"A great experience," Iannetta said. "For me to be able to catch a guy like Weav was awesome. Whatever I put down, he threw it where he wanted it."
Iannetta followed singles by Kendrys Morales, back in action at last as the designated hitter, and Mark Trumbo to load the bases in the eighth against reliever Aaron Crowe.
Peter Bourjos' infield hit against Greg Holland brought home the first run, and Aybar's rocket into the right-field corner was the decisive blow.
"Always nice to get off on the right foot," said Weaver, who began last season winning his first six starts.