For the Angels, it’s about rotation, rotation, rotation

Of the many statistics that indicate the potential strength of the Angels’ pitching rotation, most prominent are the 61-37 record, 2.97 earned-run average and 774 strikeouts that Jered Weaver, Dan Haren, Ervin Santana and C.J. Wilson combined for last season.

But the number 926 is what jumps out at General Manager Jerry Dipoto entering Friday night’s season opener against the Kansas City Royals at Angel Stadium.

That’s how many innings Weaver, Haren, Santana and Wilson combined to throw in 2011, a figure that, if repeated, would require the Angels get only 74 innings from their fifth starter — Jerome Williams or Garrett Richards — to reach what Dipoto considers a magic number for five-man rotations: 1,000.

“If you get 1,000 innings from your starters, that’s a strong indication you’re a playoff team,” Dipoto said. “I don’t think there’s been a team with five starters throwing 1,000 innings since the wild-card era that hasn’t made the playoffs.”

Not true, but Dipoto isn’t far off. In 16 full seasons (1995 was strike-shortened) since baseball broke into three divisions, eight teams have received 1,000 innings or more from five starters.

Five of those clubs, including the 2005 World Series-winning Chicago White Sox, reached the playoffs, and the three that didn’t won at least 90 games.

Although a 1,000-inning rotation is not a prerequisite for success, there is a correlation between that threshold and winning.

Since 1996, 47 of the 85 teams (55%) that got at least 1,000 innings from their starters reached the playoffs, with seven winning the World Series and seven others winning a pennant. St. Louis got 999 innings from its starters en route to last year’s title.

The theory is simple: If your starters are good and durable, they’re usually pitching into the seventh and eighth innings. That reduces the demand for long and middle relievers, who — and the Angels are no exception this season — are the weakest pitchers on the staff.

“You get your starters throwing 200 innings each,” Angels pitching coach Mike Butcher said, “you’re giving your bullpen enough rest, and everyone should be fresh and used properly.”

The signing of one star slugger, Albert Pujols, and return of another, Kendrys Morales, have raised expectations to stratospheric levels — the Angels have been picked by several national publications and websites to win their first World Series since 2002.

But if the Angels play deep into October, it probably will be because they have one of baseball’s best rotations, one that added a premium left-hander to a group that led the American League with a 3.57 ERA last season.

“It could be the greatest rotation ever on paper, but so many things happen during the year — an injury, a guy gets tired,” Haren cautioned. “I’d like to have one year together where everyone is healthy, and let’s see what we can do.”

Last September, Butcher said he’d take Weaver, Haren and Santana “over anybody’s top three in the game,” including Philadelphia’s Roy Halladay, Cliff Lee and Cole Hamels and Tampa Bay’s James Shields, David Price and Jeremy Hellickson.

Then the Angels signed Wilson, the former Texas Rangers ace, in December.

“Whether we’re one of the best rotations in the game, I believe in what we have,” said Butcher, who acknowledged he received “all kinds of flak” for his comments. “These guys are going to take the ball every fifth day and compete and give us a chance to win. What’s not to like?”

Though three of the top four are right-handed and tall — Weaver is 6 feet 7, Haren 6-5 and Santana 6-2 — their styles are different enough to give opponents a variety of looks. And all are in their prime: Haren and Wilson are 31; Weaver, who will start the season opener, and Santana are 29.

Weaver has a deceptive, across-the-body delivery, and though his fastball tops out at about 92 mph, it has late life. Weaver changes speeds on his curve and slider and has one of baseball’s best changeups.

With an 82-47 (.636) career record, Weaver has the best winning percentage in franchise history. A two-time All-Star, the Simi Valley native led the major leagues with 233 strikeouts in 2010 and finished second in AL Cy Young Award voting last season, going 18-8 with a 2.41 ERA.

Haren, a West Covina native, has a pause in the middle of his delivery that can throw off a hitter’s timing. His fastball tops out at about 91 mph, but he has excellent command of it, along with a cut fastball, split-fingered fastball and curve.

Haren was 16-10 with a 3.17 ERA last season and had fewer walks (33) than games started (34). He has never missed a start because of injury and ranks fifth among active starters with a 1.169 career WHIP (walks and hits per innings pitched) — better than Tim Lincecum, Justin Verlander and Felix Hernandez.

Santana, a native of the Dominican Republic, mixes a power fastball, which tops out at 96 mph, with a hard, tight slider and an improving changeup. He was 11-12 with a 3.38 ERA last season and threw a no-hitter against Cleveland.

Wilson, a converted reliever, has added a changeup this spring to a vast repertoire that includes a sometimes cutting, sometimes sinking fastball that hits 94 mph, slider and curve.

The Huntington Beach native has had control problems, walking a league-high 93 in 2010 and 74 in 2011, but he was a combined 31-15 with a 3.14 ERA and 376 strikeouts in those seasons for the Rangers.

“They’re unique, but it all works,” Butcher said. “They’re jelling as a staff. They challenge each other, push each other, and they work extremely hard. They want to get better. They’re not just satisfied knowing they’re good.”

What right fielder Torii Hunter likes about the rotation is “if the team is in a slump, you’re going to get out of it with one of those starters.”

Weaver thinks the friendly competition among the four will benefit the club.

“The rotation is built off guys trying to outdo each other,” Weaver said. “If someone gives up one run, you try to go out the next night and give up no runs. It’s not that you’re trying to show the guy up; you’re just getting motivation for your next start.”

mike.digiovanna@latimes.com

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