San Diego ? Dave Roberts knew desperation last October in Boston.

Here he is again, facing the possible end to his postseason.

Roberts and his San Diego Padres will disappear without a trace from the playoffs unless they beat the St. Louis Cardinals in Game 3 of their division series tonight at Petco Park.

The Padres won the weak NL West with only 82 victories, and not many people gave them a chance against the Cardinals, who at 100-62 had baseball’s best record and lead this series 2-0.

“You come in here and everyone’s expecting us to lose three straight,” Roberts said Friday. “If we can win one game and maybe kind of put the pressure on them a little bit and win another game, then things can change.

“But before we get too far ahead of ourselves, we need to win one game.”

The most notable thing the Padres have done in this series, besides losing ace Jake Peavy to a broken rib, is hit into seven double plays in the first two games in St. Louis. The Cardinals won 8-5 on Tuesday and 6-2 on Thursday.

“We haven’t had a lead in two games,” said Roberts, the center fielder and leadoff batter who will be back in the lineup tonight against right-hander Matt Morris.

The Padres will counter with right-hander Woody Williams, who made four postseason starts for the Cardinals last year, including Game 1 of the World Series against Boston.

“Something needs to spark us, and I think that we’ll do something tomorrow night,” Roberts said. “Whether it be a great play or a big hit, a two-out hit, something like that.”