Others include Matt Grzelcyk, who’s signed for one more season at $1.4 million and is one of the team’s more attractive assets.Beyond defensemen, goalie Jaroslav Halak could also attract buyers after his impressive play last season. It wouldn’t be ideal to trade either of these players, but it could clear much-needed space.Given the fact that McAvoy and Carlo provide high-quality — if not elite — defensive play and are expected to continue improving over time, don’t expect them to be on the move given the cap dilemma. In the end, though, a move likely needs to be made; the only question is who will be the one to go. As those talks continue, another RFA conundrum is brewing in Boston. Bruins general manager Don Sweeney faces trouble consider he’s tasked with locking up two important young RFA defensemen: Charlie McAvoy and Brandon Carlo, both of who could miss the start of training camp without new deals.NHL FREE AGENCY 2019: Complete list of signings for best available playersThe blueliners have developed rather quickly since the rebuild started in Boston in 2015. Carlo, who was selected in the second round of the 2015 NHL Draft, first made the Bruins’ NHL roster in 2016 and at age 20, was immediately positioned alongside team captain Zdeno Chara.McAvoy, 22, taken 14th overall the following year, actually made his professional debut in the 2016 postseason and slotted into that role with Chara; Carlo is now slotted with Krug in his left side.Since the end of the 2018-19 season, each has become a leader on Boston’s blue line. McAvoy and Carlo led all Bruins skaters in even-strength time on ice, with the former contributing to the team’s offense and power play and the latter being utilized more heavily on the penalty kill.Take another 👀at Charlie McAvoy’s OT game winner. @EASPORTSNHL pic.twitter.com/PM3RVdUQWW— Boston Bruins (@NHLBruins) February 19, 2019Their regular-season contributions carried over to standout playoff performances, and though the Bruins narrowly missed out on the Stanley Cup, both defensemen have set themselves up for a hefty payday.But as has been the pattern, cap space is cause for concern.The Bruins have roughly $7.3 million remaining in salary cap space, as per CapFriendly. McAvoy’s next contract is expected to likely be in the $6-7 million range, while Carlo is over projected AAV is about $4 million.To put things bluntly, Boston cannot afford to accommodate those annual salaries. To make room — even though Sweeney has been able to successfully sign young stars such as David Pastrnak to more team-friendly contracts in recent years — the Bruins will have to clear roughly $4 million in space.Boston has seven contracts that could be moved efficiently, creating enough cap space for Sweeney to make deals with his young defensemen. Five of those contracts belong to the team’s four best forwards and starting netminder Tuukka Rask. Fans can safely assume those names, all under contract for at least two more seasons, won’t be changing sweaters anytime soon.The other two deals belong to defenseman Torey Krug ($5.25 million AAV through 2020) and veteran forward David Backes ($6 million AAV through 2021), both of who aren’t as irreplaceable.Krug’s next contract is a subject of great intrigue at the moment. His offensive abilities — boosted by 18 points in 22 games this past postseason — should earn him more than $7 million AAV on the open market if he can’t get that money in Boston. However, Sweeney indicated earlier this summer he is not yet prepared to trade Krug, opting to at least open the regular season with him on the roster.NHL RUMORS 2019: What’s next for Ristolainen, Kreider?Moving Backes’ contract remains a more preferable yet more difficult course for Sweeney. He signed the 35-year-old forward in 2016 to contribute in a top-six role, but he hasn’t been able to quite fill those skates with seven goals and 20 points in the regular season. His lackluster play continued into the postseason, and he found himself a healthy scratch for the final three games of the Stanley Cup Final.Backes’ cap hit makes him a less than ideal trade option unless the Bruins give up a top prospect and/or draft picks to sweeten the pot. Buying out his contract will not provide Boston meaningful savings until next season, and even burying him in the AHL will only alleviate about $1 million.So, what can be done?The answer may lie in the Bruins’ bottlenecked blue line. Come fall, they will have nine total defensemen who can play NHL minutes, as well as prospect Urho Vaakanainen who can easily challenge for a full-time roster spot. With an influx of defensemen, Boston potentially has the option to make some moves with those pieces.Bruins first round pick Urho Vaakanainen scored his first goal in the Bruins system in today’s Providence Bruins game vs. Springfield.The #18 overall pick in ’17 also added an empty netter later in the game. He spent two games in Boston earlier this [email protected] #NHLBruins pic.twitter.com/MquDpab8p5— Ian Steele (@ISteeleABC6) March 4, 2019A couple of possible trade candidates could be John Moore (2.75 mil AAV through 2023) or Kevan Miller (2.5 mil AAV through 2020), but the former was a healthy scratch a number of games last season and the latter is coming off a series of injuries. Several NHL clubs are playing the waiting game.At the moment, a number of teams are in the throes of negotiating with a number of highly-valued young RFAs — the most prominent being Maple Leafs forward Mitch Marner, who has been the subject of rumors throughout the offseason.