The Dodgers have opened discussions with Ned Colletti on a long-term contract extension, which could put him in position to become the team’s longest-serving general manager since Al Campanis.

Dodgers Chairman Mark Walter said he did not know the details of the discussions but confirmed a new deal is on the table.

“That’s my understanding,” Walter said.

Colletti declined to comment. Dodgers President Stan Kasten also wouldn’t comment, citing his policy of not discussing contractual issues involving team executives.

“People should regard our management as stable and permanent,” Kasten said.

The guaranteed portion of Colletti’s current contract expires at the end of this season, although the deal includes mutual options. Colletti signed that deal with Frank McCourt, who sold the Dodgers to Guggenheim Baseball Management in May.

After a team is sold, the new management often installs its own general manager. However, when Kasten became president of the Washington Nationals in 2006, he retained General Manager Jim Bowden.

The Dodgers open a three-game series in San Francisco on Friday, trailing the Giants by 41/2 games in the National League West.

The Dodgers also trail the St. Louis Cardinals by 11/2 games for the second and final NL wild-card spot. The Cardinals visit Dodger Stadium for a four-game series next week.

Walter said he was impressed by Colletti’s diligence in building — and rebuilding — the recent nine-player trade with the Boston Red Sox. He said far more went into the deal than Guggenheim’s ability to absorb a quarter-billion dollars in the salaries of Adrian Gonzalez, Josh Beckett and Carl Crawford.

The Dodgers believed they had a deal for Gonzalez in July, but the Red Sox decided not to proceed. Colletti helped keep the trade alive through August, negotiating over the prospects the Red Sox wanted while navigating the major leaguers through the waiver process.

“That trade was not easy,” Walter said. “We talked about a lot of stuff. He worked his tail off.”

Colletti, 58, was hired as the Dodgers’ general manager after the 2005 season, becoming the seventh man to fill that position in eight years. If he were to remain general manager through the 2017 season, he would have served in the position longer than anyone since Al Campanis, who held the title from 1968 to 1987.

The Dodgers advanced to the playoffs in three of Colletti’s first four seasons, including consecutive appearances in the NL Championship Series for the first time in 31 years. McCourt then slashed payroll and later took the team into bankruptcy in an effort to retain control of the Dodgers amid a protracted divorce.

Amid those constraints, Colletti patched together a 2012 roster that had the best record in the league when McCourt left, with contributions from such bargain signings as pitchers Chris Capuano and Aaron Harang, infielder Mark Ellis and utility man Jerry Hairston Jr.

During Colletti’s tenure, several significant free-agent signings have failed to deliver, including pitcher Jason Schmidt (three victories, three years for $47 million, despite knowledge of a torn rotator cuff), outfielder Andruw Jones (three home runs, two years, $36.2 million) and infielder Juan Uribe (six home runs, three years and $21 million, with one year left).

Colletti and Kasten have emphasized the need to rebuild the Dodgers’ player development system, including an international scouting operation all but dismantled under McCourt budget cuts.

bill.shaikin@latimes.com

twitter.com/BillShaikin