NEW YORK — Throughout Brian Sabean’s 22 years of constructing Giants rosters, the word “rebuild” has not been in his vocabulary.

The focus was to supplement the roster, not strip it, and the strategy led to eight postseasons and three World Series titles.

These days, the roster is flawed and on the older side, and one of Sabean and Co.’s most challenging offseasons awaits. The Giants are heading for a possible second straight losing season, need to address an inefficient offense and will weigh all options on how to reshape their roster for 2019.

Except one, it seems. Sabean isn’t leaning toward a massive rebuild.

“We’re very beholden to a demanding fan base,” the executive vice president of baseball operations said in a Chronicle interview. “We’re used to winning. We don’t feel we’re in a position, as a result of that, to have, quote, a complete face-lift.

“So you are going to have to probably be ready to make some tough decisions. Is that going to be a strip-down or a total rebuild? That’s not the way we operated in the past.

“We still want to put the most productive product on the field that we can.”

A full rebuild would mean trading several players, enduring at least a few bottom-feeder seasons to get a flurry of high draft picks and reforming the team by relying almost exclusively on developing young players, a process that would take years.

It worked for the Cubs (2016) and Astros (2017) on their paths to winning the World Series, and it has become commonplace in today’s game, though the process of rebuilding, in some circles, has evolved into the process of tanking, losing on purpose to improve draft spots.

Many fans expressed via social media a desire for a similar blueprint, but as Sabean pointed out, it’s a fan base that has come to expect winning teams on an annual basis. Plus, such a rebuild seems far-fetched because the Giants are hamstrung by large contracts that would be tough to shed.

Though the Giants, who have fallen from the division and wild-card races by going 8-12 this month — they’re last in the league in August batting average, on-base percentage and slugging percentage — were hoping to contend deeper into the season, they’re just one win shy of last year’s total with more than five weeks remaining.

“However this turns out this year,” Sabean said, “this has been a good first step. We distanced ourselves from how last year went. I think just by virtue of all the close games that we’ve played in the one- and two-run fashion shows that if you keep the game close, we’ll get our chance to win our share of games. The offense has just been mind-boggling. It’s been so inept.”

Sabean wouldn’t say it’ll be his crew’s most challenging offseason.

“It’s not going to be any more challenging than (last) year. We were coming off 98 losses,” he said. “We’ve been beaten to a pulp as far as not staying healthy, and we’ve still been competitive.

“Is it what we want? No. But we knew this was going to be a building-block year, so it’s a start. We’ll never know what could have been because it just didn’t happen as far as health is concerned.”

Many of the core players have missed significant time with injuries, including the projected top three starters (Madison Bumgarner, Johnny Cueto and Jeff Samardzija), the projected closer (Mark Melancon) and three infielders (Brandon Belt, Joe Panik and Evan Longoria).

Plus, Buster Posey soon could undergo hip surgery after playing in pain much of the season, and Mac Williamson hardly had a chance to display his new power stroke.

“You could go right down the roster,” Sabean said. “Everybody’s had their share of bumps and bruises and missing time.”

Thanks in part to injuries, a transition to younger players already has been under way. Spots opened during the season for rookie starters Dereck Rodriguez and Andrew Suarez, along with outfielders Steven Duggar and Austin Slater and infielder Alen Hanson.

“On the positive side, I don’t know where we’d be without our second line of defense, which buoyed our hopes and kept us competitive,” said Sabean, also mentioning Reyes Moronta and Gorkys Hernandez. “You can go through anybody who’s a young player with minimum service time. Guys with little major-league experience contributed so much.”

If Andrew McCutchen is traded and Posey has surgery soon, more spots will open with September roster expansion.

“Put it this way,” Sabean said. “We’re going to be judicious about who we call up for the right reasons. If it’s deemed necessary or prudent to go with some younger folks more days than not, maybe we’re prepared to cross that bridge.”

In the meantime, there’s a season to finish. The Giants, who beat the Mets 3-1 on Thursday behind Bumgarner, who pitched eight solid innings and hit an RBI double, are nine games out of first place with 33 to go.

“We’re trying to figure out going into next year how leaky the boat is,” Sabean said. “We’re a leaky boat. That’s why we’ve never been more than five games over or under .500.

“So therein, how do you reconstruct your roster to improve your chances next year against, as you know, a very tough division? The National League, the sands have shifted the last couple of years since we went to the playoffs in ’16.”

John Shea is The San Francisco Chronicle’s national baseball writer. Email: jshea@sfchronicle.com Twitter: @JohnSheaHey