OAKLAND, Calif. – When Byung-Hyun Kim blows a postseason assignment, it’s no surprise. When the Oakland Athletics win with a bunt, it’s practically unprecedented.

Ramon Hernandez dropped a perfect bases-loaded bunt with two outs in the 12th inning, scoring Eric Chavez with the winning run to lift the A’s over the Boston Red Sox 5-4 in their playoff opener Wednesday night.

At 4 hours, 37 minutes, the game was the longest in Oakland’s postseason history, and it ended in the most improbable way: with the hard-hitting A’s executing a small-ball play to eke out a run.

Erubiel Durazo hit a tying single with two outs in the ninth to knot the game at 4.

Durazo, who had an early two-run double against Pedro Martinez, tied it with a hit off Alan Embree.

Boston’s latest postseason troubles started with Byung-Hyun Kim, the noted postseason misadventurer whose struggles nearly cost Arizona the World Series two years ago.

Kim, who relieved Mike Timlin to begin the ninth, walked a batter and hit another before Embree replaced him with two outs. Durazo followed with a clean single to center, scoring pinch-runner Eric Byrnes to the delight of most of the 50,606 fans in the packed Coliseum.

Martinez left after seven innings with a 4-3 lead, narrowly outpitching Tim Hudson in a duel that was all but forgotten by the late innings.

Todd Walker nearly propelled the Red Sox to the win with two homers, but Boston’s bullpen made another mistake in a season full of blown assignments.

In his first postseason game, Walker hit a solo homer in the first and a two-run shot in the seventh. The journeyman second baseman had four hits.

Martinez and Walker were the stars of the first seven innings. Martinez still remained unbeaten in his playoff career, but he didn’t get the win.

Martinez yielded six hits and four walks in seven innings, throwing a season-high 130 pitches. But Boston’s imposing ace was never far from trouble: He allowed three runs in the third, threw out a runner at home in the fifth and barely escaped a bases-loaded jam in the seventh.

Jason Varitek also homered and reached base four times for the Red Sox, who tagged Hudson for 10 hits and three runs. The damage could have been worse, but Manny Ramirez stranded five runners while going hitless in his first five at-bats.

Miguel Tejada had a run-scoring single for Oakland, which emerged from a mediocre offensive season to tag Boston’s imposing left-hander for three runs in the third.

Durazo, who set career highs in nearly every offensive category this season despite a prolonged second-half slump, got the biggest hit in Oakland’s third-inning rally against Martinez.

After seldom-used outfielder Chris Singleton hit a one-out double, Mark Ellis walked. Durazo then drove a pitch into the right-center gap, scoring both runners.

Tejada, who batted .143 in the division series last season, followed with a single up the middle. Tejada was caught off first base to end the inning, but Martinez appeared perturbed as he left the mound.

The A’s had a chance for another run in the fifth when Ellis singled and advanced to third on Martinez’s errant pickoff attempt, which rolled into Oakland’s spacious foul territory – but Martinez threw out Ellis at home on Durazo’s grounder back to the mound.

In the early innings, the fans got a good taste of the series’ intriguing clash of styles.

Boston’s offense led the majors in several categories and broke the major league record for slugging percentage, while the A’s depended on their perennially dominant pitching staff, which led the AL in ERA despite losing Mark Mulder to a broken leg in August.

The Coliseum was packed with fans who hung banners and posters around the patriotic bunting that decorated the stands. With a marquee pitching matchup, Oakland expected a sellout crowd – in sharp contrast to last season, when the A’s had smaller, quieter crowds for the first two games of their division series against Minnesota.

The outfield was a mess of grass, sand and sod despite serious repair efforts following the Oakland Raiders’ victory over San Diego on the same field last Sunday.

AP-ES-10-02-03 0219EDT