It's one of the truisms of the sport that if Wayne Gretzky can be traded, anybody can be traded.
Nobody—least of all a prospect with little or no NHL experience—is completely immune to trade rumors and the possibility that his general manager will see the upside in moving him down the line. However, there are a combination of factors that can make a player almost untouchable.
Generally, it's a combination of the simple rules of supply and demand. Prospects with the potential to be true difference-makers are in low supply; therefore, as a rule, the better the prospect, the less likely he is to be traded. Demand is the other half of the equation. A player like Evgeny Kuznetsov is undeniably talented, but with Washington's collection of talent up front, they arguably need to keep him less than the Calgary Flames need to hang on to a player like Sven Baertschi.
It's important to note this isn't an ordered list of the best prospects; just the ones that are most desperately needed by their current teams. So who is on the list? Let's take a look.
How acquired: 17th overall pick in 2012 NHL draft
What the player brings: While his skating is considered below-average, the rest of Hertl's skill set is extremely impressive. Here in part is how Hockey Prospectus writer Corey Pronman described him in his look at San Jose's top 10 prospects:
Hertl is an immensely-skilled player who brings multiple dimensions to his game. His puck skills are high end, he has a high level of creativity, and he can be a nuisance for defenders to check, even for a big man. Hertl is also a pretty smart two-way player, with the vision to make plays in the offensive end and the defensive skills to play against good players and kill penalties effectively. He has a big body, he can protect the puck well, and he will grind out battles in the corner.
What the team needs: San Jose has good young forwards, but for the most part, they're already in the NHL. None of their other prospects come close to having the same level of offensive potential as Hertl does. More than that, Hertl's dirt cheap—even if he hits all his performance bonuses over the next three seasons, he'll be paid less than $1.5 million per year, and he's more likely to be in the high six figures.
How acquired: Seventh overall pick in the 2011 NHL draft
What the player brings: Scheifele was a controversial pick, coming as he did with the highly touted Sean Couturier still on the board. While Couturier made the jump to the majors more quickly, Scheifele has lit up the Ontario Hockey League over the last few seasons. In the early going, he seems to have found an NHL home on a very good line with Evander Kane and Devin Setoguchi. Through two games this season, he has a goal and an assist.
What the team needs: The Jets need Scheifele to develop into a first-line center. Bryan Little is a very good player, but on a contending team, he's probably at the pivot position on the second line. He's the best of the lot and Winnipeg doesn't really have another center prospect with this kind of upside.
How acquired: 13th overall pick in the 2011 NHL draft
What the player brings: Baertschi has a little more experience than most of the players on this list, with 25 NHL games played over the last two seasons. Last year, he really impressed in a 20-game stint in Calgary, scoring at a 41-points-per-82-games pace after being the most consistent threat on his AHL team as a rookie professional.
What the team needs: Calgary needs everything, and if Baertschi can develop into a top-line offensive presence, it will mean a lot for the Flames' rebuild.
How acquired: Seventh overall pick in 2013 NHL draft
What the player brings: Nurse is a physical, 6'4" defenseman with offensive ability. Those aren't exactly common. Through three games with the OHL's Sault Ste. Marie Greyhounds, Nurse led the team's blue line in scoring with three points, a significant uptick from last season, when he was stuck behind a pair of distinguished older prospects (CHL defenseman of the year Ryan Sproul and team captain Colin Miller).
What the team needs: While their NHL roster is short on good young defenders, the Oilers actually have a prospect system reasonably stocked with defenders, with players like Oscar Klefbom and Martin Marincin headlining a deep group. However, Nurse's unique blend of talent includes nastiness and shutdown ability that the team both highly values and somewhat lacks.
How acquired: Second overall pick in 2012 NHL draft
What the player brings: Murray earns praise for his maturity and puck poise; while perhaps not the offensive game-breaker other top picks are, he plays a brilliant two-way game for his age and projects as a guy who can be relied on in all situations.
What the team needs: The Blue Jackets could really use a 25-minute-per-game defensive workhorse that can be used in all situations. Jack Johnson is their top defender by ice time in the early going, but despite a fairly extensive reputation, he isn't an ideal fit in the role. When he's on the ice, his team tends to get badly out-shot.
How acquired: Fifth overall pick in 2012 NHL draft
What the player brings: A highly skilled defenseman who scored at a point-per-game rate in his injury-shortened draft year, Rielly never had any chance at flying under the radar in Toronto. Former general manager Brian Burke made it clear immediately that the Leafs thought they had found a very special player, telling TSN's Jonas Siegel that he was first overall on their list:
We had this kid rated one. Wouldn't say that if it wasn't true just to build up the pick, but this is a guy [that] had we had the first pick in the draft we would've taken him. Once the Islanders announced their pick there was no discussion at the table, there was no hesitation, it was punch that name in the computer as soon as they tell us.
What the team needs: The Leafs aren't exactly bereft of good defensemen. But with Dion Phaneuf both a lightning rod for controversy and a pending free agent on a team that struggled to get under the salary cap this year, they could very much use a cheap, young player who could be a top-pairing option in the next few years. Some would point to Jake Gardiner, but they would find themselves at odds with head coach Randy Carlyle. If Rielly is sent down early enough this year, the Leafs can look forward to keeping him under contract for under $2.0 million per year until 2017.
How acquired: Sixth overall pick in 2013 NHL draft
What the player brings: Monahan doesn't come with a lot of flaws. Some scouts have critiqued his skating, and it's fair to ask exactly how high his offensive ceiling is, but the fact is that he plays an extremely well-rounded game for his age and was head and shoulders above his OHL teammates last season. Monahan led the team with 78 points; nobody else had more than 40.
What the team needs: The Flames' center depth isn't exactly the envy of the NHL. Mikael Backlund is a good young player, but he isn't the first-line center of anybody's dreams. In the Flames organization, Monahan's the only player who really looks like he might eventually be a plus player in that role.
How acquired: Third overall pick in 2013 draft
What the player brings: A ridiculous talent, Drouin scored more than two points per game in the Quebec Major Junior Hockey League over both the regular season and the playoffs. This was a guy who was in discussion as the 2013 draft's first overall pick. He also had an impact in his draft year for Team Canada at the World Juniors, which is something of a rarity given that Canada can afford to only bring older players to the tournament.
What the team needs: But wait a minute. Didn't this guy just get sent down? If he's so special, why is he back in junior? Here's what Steve Yzerman told the Tampa Bay Times' Damien Cristodero:
We think he's an incredible talent, a very intelligent hockey player, great hockey sense, great vision. We just feel he's better served by playing another year of junior hockey. I don't want him being in and out of the lineup. I don't want him playing limited minutes. Our assessment was he's better off playing another year of junior hockey, hopefully playing for Canada at the World Junior Championships and developing there.
It's a rational take, but it's hard not to wonder if team need is coming into play a little here. The Lightning have crazy talent in their top six—including the NHL's first- and second-leading scorers last year—so there likely isn't the same kind of pressure to get Drouin into the lineup immediately as there would be with a less dynamic team.
How acquired: Second overall pick in 2013 NHL draft
What the player brings: The Panthers raised some eyebrows when they took Barkov second overall, passing on more high-profile players like Seth Jones and Jonathan Drouin. But that's a testament to the player they feel he can become. Barkov, who just turned 18, is already listed at 6'3", 209 pounds and has been scoring at a ludicrous pace playing against men in Finland over the last two seasons.
What the team needs: Right now it's a toss-up as to which of Barkov or one of two returnees—Marcel Goc and Shawn Matthias—is the Panthers' first-line center. That says basically everything that needs to be said about the team's need for help at the pivot position.
How acquired: First overall pick in 2013 NHL draft
What the player brings: If he were a few inches taller and a few pounds heavier, the short answer would be "everything." MacKinnon has been tabbed as a future star for years now, and he has done nothing to really cast doubt on those expectations.
Bleacher Report broke down his ridiculous talent over the summer.
What the team needs: Ordinarily, this would be a case of a superb prospect being something of a luxury for a team already stacked at the pivot position. Before adding MacKinnon, Colorado could boast a top three at centre of Matt Duchene, Ryan O'Reilly and Paul Stastny; an abundance of riches.
But MacKinnon is a special player, the kind every team needs, which is why O'Reilly's now playing wing.
How acquired: Fourth overall pick in 2013 NHL draft
What the player brings: Nashville had to be thrilled when the presumptive first overall pick for much of the season fell into its lap at fourth overall. The coaching staff has demonstrated its appreciation by treating the (just barely) 19-year-old as an all-situations defender, as he's playing more than 22 minutes per game, with heavy time on both special teams.
What the team needs: The team needs good defensemen right now.
While the Predators have a (well-deserved) reputation for developing blueliners, many of those have left Nashville to pursue big dollars elsewhere. After Shea Weber, the current group is short on experience and desperately needs its young defenders to excel.