Zipping through its O'ahu Interscholastic Association baseball opener, Roosevelt blanked Castle, 2-0, yesterday at Stevenson Middle School Field behind a three-hitter by senior lefty Kelson Okimoto.

The only runs in the 75-minute pitchers' duel between Okimoto and Knights ace Pulama Silva came in the bottom of the third inning, when Casey Tanabe scored on a fielder's choice grounder to short and Aaron Yamane scored on Zach Hamasaki's sacrifice fly to left field.

That was all the run support necessary for Okimoto, a crafty left-hander who lists himself at 5 feet, 4 inches tall.

"I knew from the beginning it was going to be a tough game, so I just needed to throw strikes and keep the ball down, let my defense make the plays," said Okimoto, who finished with three strikeouts and three walks. "I was mostly just changing speeds with my fastball."

The defensive support included a catch of Brian Raines' long drive to center field by Hamasaki to end the top of the fourth inning and a leaping stab of Keola Jarret's line shot by second baseman Yamane.

The support was needed because Silva, a right-hander, pitched a two-hitter with nine strikeouts and only one walk.

"He's good, he's one of the best pitchers in the East (Division)," Rough Riders coach Craig Arakawa said. "We just wanted to put the ball in play and see if we can make things happen."

That break came in the bottom of the third.

Tanabe led off with a walk, then advanced to second on an errant pickoff throw and to third on Yamane's bloop single to right. Tanabe then scored when a fielder's choice throw home was late and wide, allowing Yamane to advance to third. Yamane then came home on Hamasaki's fly to left.

"We're not sharp on defense," Castle co-coach Chad Uyehara said. "We had some baserunning miscues, too."

Okimoto picked off the runner who was hit by a pitch to lead off the fourth inning, and the Knights had a runner in scoring position in the sixth wiped out when the hitter was called for batter's interference for the final out.

"That was crucial, because it was only 2-0, and if it's 2-1 then it's a different game," Uyehara said.

But Uyehara added that Okimoto did a good job of keeping the Knights off-balance throughout the game.

"He was tough today," Uyehara said. "He mixes his pitches up well; he changes speeds with his fastball and he has a good slow curve. And he stays ahead of you."

Arakawa said Okimoto was consistent throughout nonleague play, which included six innings pitched against 'Iolani.

"He's not a fireballer," Arakawa said, "but he knows how to pitch."

Both coaches said pitching becomes even more important this season, since the OIA split into Division I and II for the first time. That means perennial powers like Roosevelt, Castle, Kailua, Kaiser, Kalani and Moanalua will play only each other and won't be facing struggling programs like Farrington, Kaimuki and McKinley.

"It's gonna come down to pitching staff depth," Arakawa said. "It should toughen everybody up for the playoffs."

CASTLE (0-1) 000 000 0 — 0 3 2

ROOSEVELT (1-0) 002 000 X — 2 2 0

Pulama Silva and Coby Agres; Kelson Okimoto and Tyler Nitahara. W — Okimoto L — Silva.

Leading hitters — Castle: Kris Kahanu double.

Reach Wes Nakama at wnakama@honoluluadvertiser.com.