Nothing's certain until it's certain, but according to Baseball Prospectus's Playoff Odds Report, the San Francisco Giants have a 99.4% chance of making the postseason, and the Oakland Athletics are not far behind at 92.9%. And so, both teams are getting their postseason tickets ready for sale with some degree of confidence. While season ticket holders for both teams started buying their postseason strips a few weeks ago, now everyone else can get in on the action.
The A's postseason tickets will go on sale on Monday, September 17, at 10 AM, by phone, online, and at the Oakland Coliseum box office. These are tickets for a possible wild card playoff game, which would be held on Friday, October 5 -- and for the two or three first-round playoff games to be scheduled between Saturday, October 6, and Friday, October 12. Which of those games would be in Oakland, and what time they'll happen, would be determined much closer to the actual event.
Tickets are as little as $10 for the Plaza Reserved sections above the bleachers. But be forewarned: the A's are using "dynamic pricing" and those dollars could go up if demand warrants it.
The Giants have many more season ticket holders than the A's, so they're not selling single-game tickets for the postseason outright. Rather, they're letting people put their names into a drawing for the right to purchase tickets. Registration has started for the first round of playoff games -- the signup closes at 9 AM next Thursday (9/20).
The NL's wild card playoff game is also on Friday, October 5. But with a seven-game lead in the West as of today, the Giants are more likely to go straight to the division series. As with the NL, the window is between Saturday, October 6, and Friday, October 12. MLB has a complete schedule of postseason dates here.