WASHINGTON - General manager Sandy Alderson and manager Terry Collins have yet to prove that they're a winning combination. Nevertheless, convinced that a turnaround is near after four years of a painfully slow rebuilding project, the Mets on Tuesday officially retained the tandem.

Alderson, 66, agreed to an extension that runs through the 2017 season. Collins, 65, stands on thinner ice. He enters the final year of his contract as a lame duck, with only a team option in place for 2016.

Still, the Mets' core leadership duo will remain intact for the start next season, one that carries higher expectations with the expected return of ace Matt Harvey after a year recovering from Tommy John surgery.

"We're very happy with the process that's in place, the development of our players," chief operating officer Jeff Wilpon said. "And the overall direction we're taking to get to the next level."

Alderson was hired after the 2010 season, and one month later, he promoted Collins to manager after he spent the year as the club's minor-league field coordinator. The collaboration has produced a 301-341 record with no winning seasons, partly because the franchise shed nearly $60 million from payroll.

Alderson has bolstered the farm system and overseen the development of an enviable stable of young arms. His free- agent signings have been mostly lackluster, an area that he admitted needs improvement. But Alderson's trades have yielded core pieces such as Noah Syndergaard, Travis d'Arnaud and Zack Wheeler.

"We need to translate the progress that we've seen in the organization and across the franchise into more wins," Alderson said. "But I don't think we're that far away. I really don't believe that this is going to take a giant leap to get to a playoff-competitive level, and I hope I'm right about that."

The Mets entered Tuesday night's game against the Nationals with a 76-80 record, two losses away from the fourth straight losing season under Alderson's regime, and the sixth straight overall.

"Next year, we'll be in the hunt," said Collins, who earned praise from Alderson. "There's no doubt in my mind."

Alderson said the Mets must win 10 to 12 more games to achieve postseason competitiveness, though he was murky about how he intends to bridge that gap. Wilpon struck a familiar refrain, insisting that the Mets will have enough "payroll flexibility" to improve the team via free agency or trades.

But aside from rhetoric, the franchise has offered no indication of growing payroll much past the $85-million mark.

Even Alderson and Collins offered hints that the Mets' plan to improve will hinge mostly on the players they already have on the roster. In addition to Harvey's return, the Mets also expect closer Bobby Parnell to be healthy. They also must get bounce-back seasons from David Wright and Curtis Granderson.

"The wins are right there and that's without additions," said Collins, whose coaching staff likely will remain mostly unchanged. "The pieces are here."

Though shortstop and leftfield remain obvious areas in need of an upgrade, Alderson declined to specify his needs entering the winter. He also hinted that the Mets could wait out the free-agent market, a common tactic for price-conscious clubs looking for bargains.

Nevertheless, Wright credited Alderson and Collins for creating a reason for optimism for 2015.

"We've gotten ourselves to a point where I think we're going to be a very good team next year," Wright said. "We finally have gone through these rougher years where the expectations that we have on ourselves moving into next year should be pretty high."