ANAHEIM -- A representative of the A's public-relations department passed out ballots on Tuesday to select members of the media who help determine the American League's monthly award winners.

Upon hearing that his name was on the Rookie of the Month ballot, right there along with nationally known newcomers such as Evan Longoria of the Rays, Jacoby Ellsbury of the Red Sox and Joba Chamberlain of the Yankees, A's reliever Brad Ziegler shook his head a little -- and smiled a lot.

"A month ago I was just hoping to be called up," Ziegler said before the second game of Oakland's three-game showdown at Angel Stadium. "There's a lot of great rookies in the American League this year, so just to be mentioned with them is pretty special in itself."

Yet, there's no question that Ziegler, a 28-year-old right-hander with a submarine style delivery reminiscent of former A's righty Chad Bradford, belongs in such company.

After starting the season at Triple-A Sacramento and posting cartoonish numbers -- 2-0 with eight saves, a 0.37 ERA and an opponents' batting average of .174 -- in 19 appearances for the River Cats, he's been even better for the A's since being called up on May 30.

Ziegler, who worked two perfect innings on Tuesday, has made 14 appearances without allowing an earned run over 15 innings, putting him two-thirds of an inning away from setting Oakland's record for the most scoreless innings to start a career. Steve Chitren set the mark at 15 1/3 innings in 1990.

"He's been incredible," said A's starter Justin Duchscherer.

He's also been something of a shot in the arm for Oakland's bullpen, too. Although the overall numbers remain impressive, with a record of 13-7 and a 3.28 ERA, they've taken a hit in the wake of injuries to early season standouts Santiago Casilla and Joey Devine.

Casilla started the season with a 17 1/3-inning scoreless streak, but he struggled before suffering a right elbow injury that put him on the disabled list May 16, and he hasn't looked quite the same since returning to action June 19. Since the scoreless streak ended, he'd allowed six earned runs on 10 hits over four innings in six appearances through Monday.

Devine, who was 3-0 with a 1.23 ERA before being put on the DL with right elbow inflammation, isn't expected back until after the All-Star break.

Oakland's bullpen, prior to getting a breather thanks to Greg Smith's complete game on Monday night, had gone 1-2 with two blown saves and a 5.19 ERA in its previous 14 games.

The key to Ziegler's success is no mystery. He keeps the ball down, throws a lot of strikes and gets a ton of ground balls.

"That formula would work well in the fifth inning or the eighth inning," A's manager Bob Geren said, and that explains why Ziegler probably leads the Majors in bullpen innings -- i.e., times he had to get "hot" in anticipation of an appearance in the game that never materializes -- in the span since he was called up.

"I don't mind it, really. It's kind of encouraging, because it means they trust me," Ziegler said. "And at the same time, if I eventually don't get into the game, it means the starters are getting out of the jams that got me up hot in the first place.

"The guys in the bullpen have been telling me to just stand on the [bullpen] mound whenever someone gets in trouble to kind of calm things down."