By Matt Dolloff, CBS Boston

BOSTON (CBS) — The Boston Bruins may be done playing hockey for 2016-17, but that doesn’t mean it wasn’t a successful season. Despite the disappointment of losing a winnable playoff series to the Ottawa Senators, the future is bright in Boston – and if just a few of their many young prospects can contribute next year, the team doesn’t have many key spots to fill in the offseason.

But GM Don Sweeney does have some work to do.

Among the successes of the 2016-17 was the surprisingly quick emergence of Charlie McAvoy, who at 19 years old played well beyond his years in a playoff cameo for the Bruins. They may well have their No. 1 defenseman of the future, which will make the transition away from Zdeno Chara much easier to handle. They also got valuable contributions from 20-year-old defenseman Brandon Carlo, who could be the team’s future shutdown blue liner.

There are some glaring holes that the Bruins need to fill on their roster – a second-line left wing and a more reliable backup goaltender are among them – but if they can find the right pieces to fit in and get more help from their prospects, next season could see the Bruins taking another big step toward becoming a legitimate Stanley Cup contender once again.

Here’s a look at what is likely on the Bruins’ to-do list this offseason:

Find a more reliable backup goalie

Tuukka Rask might be a trade candidate if the Bruins wanted to clear salary cap space, but that is unrealistic and would have potential to be highly counterproductive to the Bruins’ quest to get better in goal. It’s far more likely that the Bruins explore the market for a backup goalie to upgrade over Anton Khudobin, or at least give him some competition in camp.

President Cam Neely admitted in his end-of-season presser that Rask simply isn’t durable enough to start 60-plus games and that the Bruins will need a better backup who can spell Rask more often to keep him fresh.

“Just based on what we’ve seen in the past couple of years, we realize you just can’t overplay Tuukka,” said Neely. “So we do have to really target a backup goalie who can play a certain amount of games that’s going to give us chances to win and give Tuukka a chance to get back in and play another stretch … the backup goalie is an area that we need to focus on.”

Although Neely said he expects a quiet free agency period for the Bruins, it may be the only avenue they have to add a decent goalie who can back Rask up. Pending unrestricted free-agent goalies like Brian Elliott, Reto Berra, Ondrej Pavelec, or Jhonas Enroth could be on their radar.

Add a second-line left wing

If Neely changes his mind and reverses course on the free agency talk, the Bruins will have no shortage of veteran UFAs who they could sign on a short-term deal as they wait for younger prospects to develop. Brad Marchand is obviously entrenched as the top-line left wing, but after him there is much to be desired.

The Bruins certainly want to add someone with some skill and finishing ability to part next to David Krejci, who could have either David Pastrnak or David Backes flanking him on the right. If they can keep the term under three years, they could look at a veteran like Patrick Sharp, Chris Kunitz, Milan Michalek, or Thomas Vanek.

But of course, ideally the Bruins don’t have to tie up any more money in forwards on the wrong side of 30, even if it is for just one or two years. First-round pick Jake DeBrusk could be ready to step in and fill the role next season; the 20-year-old finished fifth among all AHL rookies in scoring with 49 points for the Providence Bruins. He could give them the scoring touch they’re looking for – and do it at nearly half the age of a veteran free agent at a fraction of the price.

Find Charlie McAvoy’s defensive partner

McAvoy was hugely impressive in his first six games with the Bruins, which just so happened to be in the playoffs. He played a lot on a pairing with Chara, but Bruce Cassidy recently said on Toucher & Rich that he likes Chara to be paired with Carlo – which leaves McAvoy without a defined defensive partner.

The 19-year-old looks like he could excel with anyone, but he is a right-shot defenseman so he would ideally be paired with a left-shooting blue liner. Unfortunately, the current roster only has Joe Morrow to fill that role.

Torey Krug would be a logical choice to pair with McAvoy, but he is best suited on a pairing with Kevan Miller or Adam McQuaid (whoever isn’t drafted to Vegas) to complement him with size and defense. The Bruins may be left with no choice but to hope that one of their left-shot defensive prospects steps up: keep an eye out on the progress of Jakub Zboril, Jeremy Lauzon, Matt Grzelcyk, and Rob O’Gara through the offseason.

Continue to draft on defense

The Bruins certainly have a bona fide top-pairing defenseman of the future in McAvoy. Carlo already looks promising and there are still plenty of other young prospects who have a chance to pan out like the aforementioned Lauzon, Zboril, and Grzelcyk. But that’s no reason to stop drafting defensemen now.

The Bruins will need replacements for all of their veteran defensemen eventually, and there’s no telling what the future will hold for Krug when his contract runs out in three years. So the Bruins would probably be best suited to spend their 2017 first-round pick on a defenseman.

Ideally, the Bruins add another defenseman with some size to complement their relatively smaller defensive prospects coming up. The 6-foot-6, left-shooting Nicolas Hague out of the OHL could be an ideal candidate. You may also want to follow the progress of prospects like Pierre-Olivier Joseph, and Finnish blue liners Juuso Välimäki and Urho Vaakanainen.

What else?

Extend David Pastrnak: The Bruins have about $10.4 million in cap space for next season right now, according to CapFriendly. But a good chunk of that will have to go to an extension for Pastrnak. The dynamic young winger has already played himself into a deal worth at least $6 million annually, and the team appears committed to him for the long haul. Expect them to hammer out a similar deal to Marchand’s with the 20-year-old sniper this summer.

Find a taker for Ryan Spooner: The 25-year-old Spooner appears to be on the outs with the Bruins front office, but he’s also a restricted free agent. This would behoove the Bruins to find some value for Spooner in a trade so both parties can move on. If they could find help at left wing or left-shot defense in a deal for Spooner, it would be a huge win for Sweeney and Neely. UPDATE: The Bruins are indeed shopping Spooner around.

Figure out who to protect in the expansion draft: This decision appears that it will ultimately come down to a defenseman. Sweeney may have to simply choose between one of the Millers, Kevan and Colin. Kevan was arguably the Bruins’ best defenseman in the playoffs and can be a reliable veteran on the back end, but the 24-year-old Colin has more upside and flashed his ability at times. This will be among Sweeney’s tougher decisions of the offseason.

What’s on your to-do list for the Bruins this offseason? Share your thoughts in the comments.

Matt Dolloff is a writer/producer for CBSBostonSports.com. Any opinions expressed do not necessarily reflect that of CBS or 98.5 The Sports Hub. Have a news tip or comment for Matt? Follow him on Twitter @mattdolloff and email him at mdolloff@985thesportshub.com.