OAKLAND, Calif. - To know the Oakland A's is to understand their success against interleague opponents. The A's aren't just spouting clichés when they say they do nothing different against National League teams, though Oakland's 81-47 interleague record is the best in the majors. What's different is that interleague play tends to heighten the elements that have sustained the A's in recent years - pitching, and improving as the season progresses. Oakland's interleague prowess and remarkable 18-0 record against NL Central teams will be severely tested during a three-game series beginning tonight against division-leading St. Louis. Oakland proceeds from there to Chicago to face the Cubs' formidable pitching staff. The A's know all about superior pitching, of course. Their starters give them an edge against virtually any team. Against NL opponents, Tim Hudson, Mark Mulder and Barry Zito are even more effective because the league is not familiar with them. Typically, pitchers facing a team for the first time have the upper hand - "if they're good pitchers," Pittsburgh manager Lloyd McClendon said. Hudson, Mulder and Zito have a combined 30-8 record against NL teams. Their .789 interleague winning percentage exceeds their overall winning percentage of .685. "Obviously, you can watch film of a pitcher and get an idea of what he's doing," A's catcher Damian Miller said. "But until you actually get up in there and see him, it's not an easy task. Especially with the pitching staff that these guys have had here the last few years. That definitely gives the advantage to the A's." It's no coincidence that other successful teams in interleague play have boasted strong pitching: the New York Yankees (77-49), Florida (73-50) and Atlanta (73-51). Timing is everything, which also has helped the A's. They are a major-league-best 47-20 in June since 2002. Interleague play begins in June, so the A's usually are approaching their peak when they match up against NL teams. The composition of the A's might be another factor. Oakland's managers during its interleague reign, Art Howe and Ken Macha, have NL backgrounds. They learned about using reserves more frequently and approaching lineups with the pitcher batting ninth. Macha pointed out that NL teams favor versatile utilitymen and relievers capable of throwing multiple innings; their AL counterparts include one-dimensional designated hitters and more situational relievers. But Macha also noted that the A's have had NL-type players, such as John Mabry two years ago, who proved handy during interleague play. Mark McLemore, who has replaced injured Eric Chavez at third base but remains capable of playing second base and the outfield, is an Oakland player fitting that profile. But the A's won't be allowed to use a designated hitter in St. Louis and Chicago, which probably will rob their lineup of Erubiel Durazo. Given Durazo's production - he leads the team with a .320 batting average and ranks third with 10 home runs and fourth with 34 RBIs - the A's could be significantly hampered. If Durazo plays, he would man first base, meaning Scott Hatteberg, who has a 14-game hitting streak and a .318 average, would sit. "I don't know if this ballclub is set up for the National League," center fielder Mark Kotsay said. "Obviously, we're going to lose a hitter out of our lineup. That's going to hurt us a little bit."