A True Test for Giants : Pro football: They’re seeking first playoff berth since 1990 but face a formidable Dolphin team in first game at Miami.

Baseball has its September. Football’s equivalent is December, the time of year when positioning for the playoffs becomes a measurable reality and not merely a distant thought.

“This is the time of year where you put it all on the line,” New York Giant safety Greg Jackson said. “There is no sense saving anything for later. There is no later.”

The stretch drive of what the Giants (8-3) hope will end with their first playoff berth since their 1990 Super Bowl season begins in earnest today when the NFC East leaders meet the AFC East-leading Miami Dolphins at 1 p.m. PST at Joe Robbie Stadium.

For those who have criticized the Giants’ inconsistent performances and scoffed at their Super Bowl chances, this game should go a long way toward establishing their rank among the NFL elite.

The Dolphins, despite losing quarterback Dan Marino and Scott Mitchell because of injuries, have the league’s best record at 9-2, having beaten the defending Super Bowl champion Dallas Cowboys, 16-14, on Thanksgiving Day.

And while this will be the Giants’ first-ever regular-season visit to Joe Robbie Stadium, there is enough precedent to indicate trouble awaits. The Dolphins are 11-0 in Miami against NFC East teams since the AFL-NFL merger in 1970, and they are 11-0 against all NFC teams since moving to Joe Robbie Stadium in 1987.

“This is a good challenge for us,” said Giant Coach Dan Reeves, whose team lost a preseason game, 23-17, at Miami on Aug. 28. “They just don’t make mistakes. They try to control the ball and keep it away from you. They’re not going to beat themselves.”

The Giants, riding a three-game winning streak over division foes Washington, Philadelphia and Phoenix, have two objectives today to help their December run begin on a positive note. First, they must re-establish a running game that has been top-rated in the NFL most of the season but managed only 46 yards against the Cardinals last week. “It’s no secret that we’ve got to run the ball to be successful,” running back Rodney Hampton said. “That’s the way it’s always been around here.”

The Giants also must contain the Dolphins’ second-ranked offense, particularly their passing game, which accounts for 255.2 yards per contest. Accomplishing either goal figures to be difficult.

The Dolphins’ improving run defense ranks sixth in the NFL and is on pace to set a franchise record. Miami has given up only 92.5 yards rushing after giving up an average of 100 yards per game last year, the fewest in team history. Most of the run support comes from the linebackers and safeties. Linebacker Bryan Cox leads the team in tackles with 80, and safeties Jarvis Williams and Louis Oliver are second and third with 76 and 64, respectively.

“We got away from the running game last week because we were struggling,” Giant offensive coordinator George Henshaw said. “Like anything else, if you’re not having success with it, then you try something else. But we have to get back to the running game. We just have to be more consistent at it.”

The Dolphins’ passing game has remained consistent despite a revolving door at quarterback. Steve DeBerg looks for his third consecutive victory as a starter after taking over for Mitchell, who separated his shoulder Nov. 14. DeBerg, the NFL’s oldest player at 39, has thrown for 539 yards in his two starts, including a 287-yard outing in the snow and sleet in Dallas.

“No matter who is the quarterback, we seem to keep rallying behind him and keep winning ballgames,” said wide receiver Mark Ingram, the former Giant who signed as an unrestricted free agent with the Dolphins. “Fortunately, we’re blessed with enough talent around here where we’re not depending on one or two people to make a lot of plays.”

This is only the third regular-season meeting between the two teams, but the Giants are concerned with a few familiar faces in the Dolphins’ offense: Ingram, who has 26 catches for 501 yards (three touchdowns); former New England Patriot Irving Fryar, who leads with 43 catches for 674 (five touchdowns); and two former Eagles, running back Keith Byars and tight end Keith Jackson.

Byars, a dual threat as a runner and receiver, had an impressive day against the Cowboys, accounting for 157 total yards from scrimmage, including a 77-yard touchdown run in the first quarter. His sprint tied Leroy Harris (197O) for the longest run in Dolphin history. Rookie running back Terry Kirby also is an important part of the passing game with 41 catches for 430 yards.

“Offensively, they’ve got an awful lot of weapons,” Reeves said. “This is the best supporting cast that (DeBerg) has ever had. He’s got a good running game that allows him to use the play-action passes and he’s got excellent receivers. He can move the ball around to any of these guys and be effective.”

“This might be the most talented football team in the NFL,” DeBerg said. “Being surrounded by skilled athletes makes me a better quarterback.”

With five games remaining, the Giants know the stakes. They have a one-game lead over the Cowboys in the NFC East they want to protect as well as keep pace with the San Francisco 49ers (8-3) for the best record in the NFC. Say what you will about their less-than-impressive victories over the Eagles and Cardinals, heading into the final month of the season, the Giants are right where they want to be.

“When it’s all said and done,” Giant defensive end Keith Hamilton said, “they don’t ask how, they ask how many.”