Role players and depth defensemen are going to be the biggest currency of the day Wednesday when the 2015 NHL free agent market opens.

A big reason for that is most of the impact players who could be free agents have already signed new contracts with their current employers. Players in the free agent class of 2016 can begin signing extensions Wednesday, so it's time to take a look at the biggest names who can become unrestricted and restricted free agents a year from now.

There are plenty of impact players on these two lists, and any number of them signing a new contract could end up being the biggest news of the day and have the greatest lasting impact on a franchise.

NOTE: The number in parentheses is the player's age when the 2016-17 season begins.

UFAs

Anze Kopitar, Los Angeles Kings (29 years old)

Kopitar is one of the top five centers in the world and along with Drew Doughty the dual engines of the Kings. The average annual value on his current contract is $6.8 million, and he'll receive a significant raise.

Steven Stamkos, Tampa Bay Lightning (26)

Stamkos is one of the two best goal scorers on the planet, and just captained a team to within two victories of the Stanley Cup. He could surpass Jonathan Toews and Patrick Kane for the highest AAV in the League, and anything below a max contract would be savings to help the Lightning sign other core players (more on that in a bit).

Mark Giordano, Calgary Flames (33)

Giordano has been one of the top five or six defensemen in the NHL in the past two seasons, and was a potential Norris Trophy/Hart Trophy candidate in 2014-15 until he got hurt. The term on his next contract will be interesting, but the Flames can assemble one of the top defense corps for years to come with Giordano, Dougie Hamilton and TJ Brodie.

Jakub Voracek, Philadelphia Flyers (27)

No. 1 centers and No. 1 defensemen are the most valuable skaters, but Voracek is on the short list for best wing in the NHL. He and Claude Giroux can be a dynamic duo for years to come. Among wings drafted in 2007 or later, Voracek is first in points in the past three seasons with 189 (one more than Kane) and fourth in points per game behind Kane, Jamie Benn and Taylor Hall.

Dustin Byfuglien, Winnipeg Jets (31)

Byfuglien is fine as a power forward when the Jets have put him there, but he's an elite defenseman, even if the numbers like his play more than the eyeballs do sometimes. Winnipeg has a lot of young talent on the way and is an emerging contender, but what happens with Byfuglien could be critical for the Jets to make a Stanley Cup run in the near future.

One of the best two-way centers in the League, but the Blues' postseason record has probably kept him from being firmly in a group with guys like Toews and Kopitar. Even if he's just outside the elite, he's incredibly valuable and a No. 1 center on many teams.

Eric Staal, Carolina Hurricanes (31)

After eight years of averaging 0.85 points per game or better, he's slipped to 0.77 and 0.70 the past two seasons. He'll be 32 early in the 2016-17 season, but his value could get a boost from an improved team around him in 2015-16.

Brent Seabrook, Chicago Blackhawks (31)

While general manager Stan Bowman is still sorting out who to keep and who to trade for next season, Seabrook is the next core player in need of a new contract. Duncan Keith, Niklas Hjalmarsson and Seabrook are one of the best trio of defensemen in the NHL, but like the forwards, trying to fit them all in the budget won't be easy.

Tomas Plekanec, Montreal Canadiens (33)

Plekanec is an underrated two-way center, but he will also be 34 in late October 2016. The Canadiens have Max Pacioretty and Brendan Gallagher signed to team-friendly contracts, which helps leave more room for Plekanec if needed.

Kyle Okposo, New York Islanders (28)

Okposo is an interesting player to monitor. His name was reported as a potential trade candidate before the 2015 NHL Draft. The Islanders have lots of young players who could become frontline guys on a title contender, but Okposo is already such a player. He's also likely due a hefty raise from his current AAV of $2.8 million.

Ryan Kesler, Anaheim Ducks (32)

Long considered one of the top No. 2 centers in the League, the advanced stats say Kesler has already slipped a little from his peak and a decline is inevitable. His defensive prowess should help his transition into a No. 3 role though.

Andrew Ladd, Winnipeg Jets (30)

One of five captains on this list (Shane Doan is a sixth) who could be UFAs next summer, he can still be a valuable top-six forward and obviously an important member of Winnipeg's leadership group.

Erik Johnson, Colorado Avalanche (28)

Johnson was having a nice 2014-15 season, and not just because of an inflated shooting percentage, before injury derailed it. He's not the only key member of the defense corps the Avalanche have to negotiate a contract with.

Alex Goligoski, Dallas Stars (31)

Goligoski has played a lot of minutes in his four-plus years in Dallas, and is an above-average but maybe not elite defenseman. He could be a veteran anchor for an otherwise pretty young defense corps in the coming years for the Stars.

Brian Campbell, Florida Panthers (37)

Campbell went from looking like a huge overpay for the Chicago Blackhawks seven years ago to being properly valued as the cap went up and as advanced stats helped illuminate his worth. His next contract will probably be much shorter in length though.

Milan Lucic, Los Angeles Kings (28)

Now that the Boston Bruins have turned him into a huge haul, the Kings have him for one year at $6 million. He was considered a top power forward, but his production has slipped in two of the past three seasons.

David Perron, Pittsburgh Penguins (28)

His arrival in Pittsburgh started great, but his production cooled as the season progressed. He's got two of the best centers in the world to play with, which could enhance his value.

He was great as both a mentor and a facilitator for Florida's group of young forwards after arriving in a trade this past season. He has said he wants to play until he's 50. If he thinks he can still play in 2016, someone in the NHL will pay him to do so.

There is also a large group of restricted free agents who are already impact players at the NHL level. Teams, and the players, have an interesting decision to make about a long-term contract versus a shorter "bridge deal" as it has become known.

Sometimes the two sides can't decide on either, and a potential RFA ends up on the move like Hamilton from the Bruins to the Flames this past weekend.

Here's a list of the top RFAs in the class of 2016:

RFAs

Nathan MacKinnon/Tyson Barrie, Colorado Avalanche

Johnny Gaudreau/Sean Monahan, Calgary Flames

Hampus Lindholm, Anaheim Ducks

Nikita Kucherov/Alex Killorn, Tampa Bay Lightning

Filip Forsberg/Seth Jones, Nashville Predators

Sean Couturier/Brayden Schenn, Philadelphia Flyers

Aleksander Barkov, Florida Panthers

Jaden Schwartz, St. Louis Blues

Morgan Rielly, Toronto Maple Leafs

Chris Kreider, New York Rangers

Ryan Strome, New York Islanders

Olli Maatta, Pittsburgh Penguins

Michael Hutchinson, Winnipeg Jets

Jared Spurgeon, Minnesota Wild

Torey Krug, Boston Bruins

Boone Jenner, Columbus Blue Jackets

Petr Mrazek, Detroit Red Wings