Not out of left field

Suddenly Juan Rivera is playing like a superhero.

Bam! The slugger powered the Angels to a victory over the Dodgers last week with a tiebreaking, eighth-inning homer.

Pow! He’s hitting .306 and is on pace for 25 homers and 88 runs batted in, which would both be career highs.

Thwap! The left fielder extended his glove over the wall at Angel Stadium last month to rob Seattle’s Russell Branyan of a homer, and he nearly took one away from Jose Lopez on a similar play three pitches later.

Rivera’s catch against Branyan prompted center fielder Torii Hunter, an eight-time Gold Glove Award winner, to flash Rivera a sign with his hand that he dubbed “the web of Spider-Man.”

“That’s respect,” Hunter said.

The transformation from afterthought to solid defender and middle-of-the-order masher, it seems, required only a bigger role -- and a healthy leg. Sidelined for most of 2007 by a broken tibia, Rivera replaced Gary Matthews Jr. as the regular left fielder about this time last season and has remained in the lineup.

The Angels were so confident that Rivera’s second-half numbers from last season -- he hit all 12 of his homers after July 2 and drove in 16 runs in his final 17 games -- were indicative of his potential that they bid farewell to veteran left fielder Garret Anderson and rewarded Rivera with a three-year, $12.75-million contract.

He has turned out to be quite the bargain. Rivera leads the Angels with seven game-winning runs batted in and is hitting .369 with runners in scoring position, second in the American League. He has five homers in his last 10 games, giving him 11 homers and 38 RBIs on the season.

“We knew he was a good player,” Angels General Manager Tony Reagins said, “and sometimes all you need is an opportunity to get out there and play every day.”

Reagins assured Rivera before the season that he would get that chance as the designated hitter or a corner outfielder. When right fielder Vladimir Guerrero suffered a torn chest muscle in April, it solidified Rivera’s spot in the lineup.

Not that Rivera has made any assumptions about playing time.

“I feel like I have to go out there and pretty much earn the right to play every single night,” Rivera said through an interpreter. “That’s the attitude I want to take right now.”

The Angels got a taste of what Rivera could do on a full-time basis in the second half of 2006, a season he finished batting .310 with 23 homers and 85 RBIs. But he broke his leg during a winter league game in his native Venezuela that December and feared the worst.

“The first thing that went through my mind when that happened was that my career was over,” Rivera said. “But then as time went on and a few days went by, I told myself, ‘I’m going to be back. I’m not done.’ ”

Turns out he was just getting started. He returned in September 2007, and last season was a productive alternative to the slumping Matthews over the final three months.

“Inside of me, I knew I could play every day,” Rivera said.

This year, he avoided April and May slumps that typically have contributed to his .263 career batting average in the first half of a season.

Dodgers reliever Guillermo Mota learned how tough an out Rivera can be late in the first game of last week’s Freeway Series. Rivera fouled off six pitches before capping a nine-pitch at-bat with a solo homer that lifted the Angels to a 5-4 victory.

“He steps in that box and doesn’t like to make an out,” Angels hitting coach Mickey Hatcher said. “He can go four for four and his fifth at-bat make an out and be mad.”

Rivera also rarely strikes out -- 22 times in 232 at-bats this season -- a rare trait among power hitters.

“There aren’t many giveaway at-bats,” Manager Mike Scioscia said. “He handles a lot of different areas because he really has quick hands. I don’t think there’s one glaring flaw that you’re going to get him on every time. I think it makes pitchers have to work for every out every time he’s up there.”

Hitters are discovering that Rivera can be just as dangerous in the outfield. He has four assists, no errors and one memorable moment May 29 against Seattle when he planted his right foot on the thigh-high padding on the wall in front of the Angels’ bullpen and stretched out his glove to deprive Branyan of a homer.

Despite his considerable impact, the soft-spoken Rivera, who turns 31 a week from today, realizes he’s still somewhat anonymous in a clubhouse that includes more celebrated teammates such as Guerrero and Hunter.

“I don’t need that type of attention,” Rivera said. “I quietly want to come over here and do my job and help the team win. . . . If I can produce for the team, that’s all the recognition I want.”

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ben.bolch@latimes.com