As frugal as they’ve been since the NHL’s free-agent market opened, the Bruins still don’t appear to have the salary cap room to re-sign Charlie McAvoy, Brandon Carlo and Danton Heinen.Trading David Backes’ $6 million salary seems the simplest solution, but that doesn’t mean it’s an easy one.

The dust has settled, but only temporarily. It has to be kicked up again this summer.

As frugal as the Bruins were when the NHL’s free agent market opened on Monday, they slid a little deeper into a curious situation in which every little bit doesn’t help, but hurts a bit.

So far this offseason: $1.85 million on Monday for forwards Ritchie ($1 million) and Par Lindholm (850,000). They spent $800,000 to re-sign Steven Kampfer. They’ve swallowed the $1.5 million shortfall in NHL salary cap estimates for 2019-20.

That’s $4.15 million -- not much money when it comes to today’s NHL, and in this case, just the cost of doing business: The Bruins needed a physical winger to replace the departed Noel Acciari, and perhaps play above the fourth line (Ritchie), they needed a left-handed center who can kill penalties (Lindholm), the salary cap is the salary cap, and a team’s gotta do what a team feels it’s gotta do.

When all was said and done, though, the Bruins had only $10.1 million in space beneath next year’s $81.5 million cap, and still had three restricted free agents to re-sign in defensemen Charlie McAvoy, Brandon Carlo and Danton Heinen.

Barring some miracle -- make that fantasy -- by which all three agree to sign very short contracts for very short money, $10.1 million won’t get all three deals done. There’s no question that McAvoy and Carlo, both already among the Bruins’ Top Four, are the future pillars of the defense corps, and the B’s see in Heinen a winger with the potential to fill nearly any hole that might pop up. As recently as Monday, general manager Don Sweeney mentioned Heinen as a potential replacement for Marcus Johnasson, the unrestricted free agent to whom they couldn’t even extend an offer because of their cap situation.

Assuming the B’s are committed to re-signing all three players, the most obvious way to create more cap space is to trade a player off the current roster. And the most obvious player for the Bruins to trade is David Backes, and his $6 million salary over the next two seasons.

Obstacles have been well documented. Backes is 35. His production has dropped from 38 to 33 to 20 points in the three seasons since Sweeney signed him to a five-year deal. Per capfriendly.com, buying out the contract would still leave whoever’s paying it with a $5.7 million cap hit for the coming season, so the savings are almost non-existent. And Backes can only be traded to eight teams in 2019-20, unless he approves a deal elsewhere.

There is still value in Backes’ experience, leadership, size (6-3, 215) and ability to play wing and center, but the Bruins don’t need those assets as much as they need money to pay McAvoy, Carlo and Heinen.

Finally, they need fourth-line players to prove capable of moving up the lineup (center Sean Kuraly is one; Ritchie, a 16-goal scorer for the Stars two seasons ago, might be another) more than they need an established -- and expensive -- player like Backes to fill a fourth-line role with Lindholm, Chris Wagner, Joakim Nordstrom, and Kuraly and Ritchie if they don’t move up. Backes’ skills may be best suited to fourth-line duty, but on a team that has let valuable fourth-liners walk rather than match other teams’ offers (Tim Schaller left last season for $1.9 million a year with the Canucks; Acciari will make $1.667 million for each of the next three years with the Panthers), $6 million is simply too much.

Sweeney said on Monday that he had Backes’ eight-team list, and acknowledged that trade talks are “a possibility … it’s on the table that we may.” The GM also said he’s trying to get representatives for McAvoy, Carlo and Heinen to the bargaining table, but that “there’s just no way to push anybody to the table, or pull anybody to the table … some of these things just take time.”

They’ll probably take a good amount of creativity, too. Just because trading Backes seems like the simplest solution to the Bruins doesn’t mean they can find another team to help them reach that solution. Any deal could involve including more players on the roster, draft picks, retaining some of Backes’ salary, or some combination of all that.

A long, dusty road lies ahead.