OAKLAND, CALIF. ? There’s nothing special about Keith Foulke.

That’s the belief of Oakland Athletics general manager Billy Beane, who thinks even the best relievers can be replaced by cheaper pitchers of roughly equal talent.

Beane values his closers, but he also values the draft picks, cash and prospects that can be acquired for them.

Yet, Foulke has emerged as the best pitcher to hold this revolving role in recent years — and the short, unimposing right-hander could be the key to Oakland’s division series against the Boston Red Sox and their own adventurous bullpen.

“I’ve been thinking about the playoffs for a long time,” Foulke said. “It’s going to be great to be out there with so much on the line. That’s what I thrive on. I want to be the guy with the ball in that situation.”

The best-of-five matchup begins Wednesday with Boston ace Pedro Martinez facing Tim Hudson at the Coliseum. With two strong starting rotations, most games are likely to be close.

That’s when Foulke has been at his most valuable for the low-budget, low-scoring A’s. Even Beane knows Foulke has been invaluable to Oakland this season.

“I think he’s having the best year for any reliever here since Dennis Eckersley,” said Beane, invoking the A’s dominant closer and former American League MVP during three straight World Series appearances from 1988-90.

While building the A’s into a small-market powerhouse with four straight playoff appearances, Beane has employed four full-time closers: Billy Taylor, Jason Isringhausen, Billy Koch and Foulke. None has been more effective than Foulke, who claimed a spot among baseball’s elite relievers in just one season with the A’s.

Foulke was phenomenal in almost every relief situation. He got 43 saves in 48 chances, and he went 9-1 with a 2.08 ERA, 88 strikeouts and just 20 walks.

If not for a slight propensity for home-run balls — he yielded 10 homers among his 20 earned runs — Foulke would have been practically unhittable. He went 7-0 with 23 saves at home, but allowed just seven runs and seven walks for a 1.80 ERA on the road.

“What he’s done is simply amazing,” Beane said. “He’s been reliable, durable and very effective. I don’t know that anybody can do more than what he’s done this season. He’s been a tremendous lift.”

It still wasn’t enough for Foulke, who has been known to criticize himself for throwing too many pitches in a 1-2-3 inning. Irrational perfectionism is just one of the factors that drives him, along with the disrespect of the Chicago White Sox’s decision to dump him last winter after six seasons in their bullpen.

“When I came here, I came for one reason — to win a division and get this team through the playoffs,” Foulke said. “I hope I can do that. It’s an opportunity that I’ve wanted for a long time.”