“If we are relying on World Cup experience, we are in trouble. But we’re not,” United Coach Ben Olsen said. (Ned Dishman/Getty Images)

Before its first playoff appearance in five years, D.C. United will peer across the field Saturday night at RFK Stadium and see an opponent armed with experience at towering levels.

New York’s Thierry Henry and Rafael Marquez have played in front of 100,000 for FC Barcelona against Real Madrid and gone to multiple World Cups. Rest assured, the first leg of an MLS Eastern Conference semifinal is not going to faze them or their well-tested teammates.

United’s most accomplished regular outside of league play is midfielder Branko Boskovic, who has represented tiny Montenegro in European competition.

“If we are relying on playoff experience, we are in trouble,” United Coach Ben Olsen said Friday. “If we are relying on World Cup experience, we are in trouble. But we’re not. We’re relying on our team being a group and a team that is really looking out for each other and finding ways to win.”

While United lacks pedigreed backgrounds — no current player was with the club the last time it appeared in the playoffs and only two have considerable postseason exposure — D.C. has performed with the poise of a steeled bunch in overcoming the late-season loss of injured star Dwayne De Rosario.

Based on seeding, No. 2 United (17-10-7) should be a slight favorite against the No. 3 Red Bulls (16-9-9), but since De Rosario went down and D.C.’s outlook dimmed, Olsen has rallied his players with an us-against-the-world mentality.

“We know everyone has New York going on to the next stage — the team with all the money and big-time players,” defender Dejan Jakovic said.

United’s underdog persona grew this week when it relinquished home field for Wednesday’s final leg, a change precipitated by Hurricane Sandy’s impact on the New York area. Instead of playing in Harrison, N.J., on Saturday and hosting the finale, United will have to win the series on the road next week.

MLS still plans to stage the second game at Red Bull Arena, which lost power during the storm. But in case of lingering problems, alternate sites are being explored, Commissioner Don Garber said.

Although each side has one home match apiece in the series, which will be decided by total goals scored, hosting the second game is preferable.

The reason: Teams take comfort playing the deciding game in front of a friendly crowd, and if the series is even at the end of the second match, 30 minutes of extra time and possibly penalty kicks commence right away.

Since MLS implemented the two-game format in 2003, though, only 7 of 36 series have been decided after regulation time.

United was widely commended for agreeing to the schedule change. “Very classy move. Incredible gesture,” Red Bulls midfielder Dax McCarty said.

The switch hasn’t troubled United or drastically altered preparations.

“Any way you cut it, it’s a home-and-away series,” Olsen said. “It’s the coaches and upper management that stress about this stuff and overanalyze things. The players are ready to get moving and play wherever the game is.”

Location wasn’t a problem down the stretch for United, albeit against weaker opponents. United closed with a seven-game unbeaten streak (5-0-2) to finish with the third-best record in the 19-team league. United has been particularly effective at home: a 16-game unbeaten streak (12-0-4) with a 2.3 goals-average since conceding a last-minute strike in a 1-0 opening loss to Kansas City.

Despite a thin playoff portfolio, United was subjected to playoff-like circumstances for two months.

“It’s been a playoff mentality for a long time now,” said midfielder Chris Pontius, who, in his fourth season, joins Jakovic as United’s longest-tenured players. “We needed to get results. It was the only way we were getting into the playoffs. The guys took a professional mentality and played beyond their years.”

Olsen was a starting midfielder the last time United appeared in the playoffs, a 2007 loss to Chicago in the conference semifinals, which culminated with a defeat at RFK Stadium.

“You can make a case we are young and naive in the playoff world, and maybe that is a good thing,” he said. “We have been battle-tested over the last [two months] because there have been some real games that were do or die.”

United and New York form MLS’s longest-running rivalry, although for many of the league’s 17 seasons one overshadowed the other and they failed to collide in the playoffs.

This is their fourth postseason meeting, with United having won each previous encounter.

This year’s three regular season meetings helped rekindle the rivalry.

Pontius recorded his first hat trick in a 4-1 home victory in April and added two more goals in a 3-2 loss at Red Bull Arena in June.

Two months later, Wilman Conde’s 88th-minute stunner spoiled De Rosario’s 100th regular season career goal in a 2-2 draw at RFK.

New York led the conference with 57 goals, topped by Kenny Cooper with 18 and Henry with 15.

United was second with 53.

While the Red Bulls would accept a draw ahead of the return leg at home, United’s game plan requires greater urgency.

“We need to continue what we’ve done here at home so far this season — put them under pressure and take the game to them,” midfielder Lewis Neal said. “It doesn’t have to be pretty, it doesn’t have to be too exciting. It just has to be about winning.”