Three weeks have passed since general manager Sandy Alderson signaled to rivals that the Mets were open for business. It was an attempt to test the trade waters, an enticement for teams to jump the market.

The response has been mostly muted, leaving the Mets to brace for a flurry of action right at the July 31 non-waiver trade deadline. That means more time to decide how to proceed.

On the surface, the decision already has been made. At 39-47, the Mets are 10 1⁄2 games behind in the race for the second wild card. If they continue on their trajectory, Alderson will be busy looking to move his veterans on expiring contracts. Closer Addison Reed figures to be the most attractive trade chip, especially with plenty of contenders looking to fortify their bullpens.

But the beginning of the second half presents an opportunity to change course. The upcoming schedule features series against the Cardinals (43-45), A’s (39-50) and Rockies (52-39), who skidded at the end of an otherwise strong first half. A surge could change the Mets’ actions leading up to the deadline.

“It’s all a fluid situation,” a team official said recently.

Without the prospects to swing the kind of impact trade that brought in Yoenis Cespedes and Jay Bruce in recent years, the Mets have two choices.

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They can play well out of the break, stand pat and hope that Noah Syndergaard and Jeurys Familia return early enough to make a run at a wild card.

Or the Mets could begin a kind of limited sell-off, an option that comes with a few complications. One is that industry executives are expecting a market that favors buyers.

So with Cespedes and their core group of pitchers still under control for next season, the Mets won’t be eyeing a teardown. Rather than rebuild, they’ll retool.

It’s why Jerry Blevins likely will stay put even though he could be one of the Mets’ more valuable trade pieces. With a $7-million team option for next season, the Mets may wind up keeping the 33-year-old lefty, one of the few bright spots of an otherwise leaky bullpen.

Bruce heads up the Mets’ potentially available position players. He’s on pace to reach 40 homers and 100 RBIs and is owed roughly $6 million for the rest of the season.

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“There are no hard feelings for me at all,” said Bruce, whom the Mets acquired at the trade deadline last year. “I understand this side of it, I’ve been a part of it. This is my third or fourth year being part of trade rumors. I will be ready for whatever happens. I get it.”

But pitchers generally will be in higher demand than the kind of position players the Mets have to offer. They include Curtis Granderson, Lucas Duda, Neil Walker and Asdrubal Cabrera, who may fetch mid-tier prospects at best.

For Walker and Cabrera in particular, the trade deadline might not actually be a deadline at all. Walker remains on the disabled list with a hamstring injury and is owed more than $8 million. And while Cabrera is owed less than $4 million, his $8.5-million team option for next season includes a $2-million buyout. Considering those contracts, both almost certainly would go unclaimed, which would give the Mets leeway to move Cabrera after July 31.

Either way, the Mets soon will have some decisions to make.

“If the organization isn’t always trying to make themselves better in the long run, then they’re doing everyone involved a disservice — the fans, the players on the team currently, everyone,” Bruce said. “Because the goal is to be good for a long period of time.”