OAKLAND, Calif. — The Oakland Athletics are in the playoffs, and they celebrated their accomplishment Monday night by bum-rushing the field and spraying champagne in the clubhouse.The Rangers, meanwhile, maybe 50 feet down the hall, remained stoic and confident that they will have the ultimate celebration this week at O.co Coliseum by winning the American League West crown.They had hoped to accomplish that Monday night, but they couldn't overcome a balk and a missed scoring chance in a 4-3 loss to Oakland that cemented the five AL teams in the postseason and eliminated Anaheim and Tampa Bay.The Rangers clinched a playoff spot Sunday and need to win one of their final two games to secure the AL West for a third consecutice year. But they likely need to win out to topple New York for the top record in the league and the No. 1 seed in the playoffs.We've got to win tomorrow (Tuesday), veteran Michael Young said. We've been playing a lot of tight games, but this team has a lot of experience in those types of games.A jittery Martin Perez allowed two runs in the first inning, including one on a mindless balk, and Oakland scored two more off him in the fifth to break a 2-2 tie.Mike Napoli homered to start the seventh, but three A's relievers retired the final nine Rangers hitters to set off the Oakland party.The Rangers weren't bothered by the A's celebration, but instead said their division rivals deserved to have fun with the franchise's first playoff appearance since 2006.Of course they're going to be out there celebrating, Napoli said. Hats off to them, but we're worried about trying to win the division. We'll see what happens.The first two A's hitters singled against Perez, who then got Yoenis Cespedes to bounce into a double play. But Perez walked Chris Carter with two outs, and Josh Reddick followed with an RBI single.After walking Josh Donaldson to load the bases, Perez started his full windup by stepping back with his right leg. But he stopped, committing an obvious balk to bring home a second run.I wasn't nervous, said Perez, who threw 19 of his 31 pitches in the first outside the strike zone. I put a little pressure on myself and then I started settling down.He retired 10 of the next 11 hitters as the Rangers came back to forge a 2-2 tie. Elvis Andrus singled in a run in the third and Young homered in the fourth, but Josh Hamilton and Adrian Beltre couldn't capitalize after Andrus' single with Mitch Moreland at third and one out.To me, that's the difference in the ballgame -- the balk and the situation where we couldn't get that run in, manager Ron Washington said.So, the Rangers are left to win today or Wednesday in the season finale to win the division and avoid having to play a one-game playoff as one of the two wild-card teams.Matt Harrison, an 18-game winner, will face Travis Blackley in a rematch of a game Thursday that the Rangers won 9-7.I wouldn't call it precarious, Washington said, My team knows what has to be done. We just got beat tonight.