Even with John Tavares, John Carlson, Paul Stastny, and James van Riemsdyk headlining a top-heavy free-agent class, the following five players easily provide the most intrigue.

Each of them has enough red flags that teams would ideally want to sign them to one-year contracts, but their upside is high enough that it will almost certainly take a multi-year deal to outbid fellow teams tempted by the ceiling.

Here are the top five boom-or-bust unrestricted free agents set to hit the open market on July 1.

Ilya Kovalchuk

Kovalchuk is set to make his return to North America after spending the last five seasons in the KHL. At 35 years old, the biggest question is if he has anything left in the tank.

The NHL is a different league from when he last played in it in 2012-13. It's faster and filled with youth. At 230 lbs, does he have enough speed to keep up?

He has remained prolific overseas, scoring 31 goals with 63 points in 53 games this past season, but the KHL is a much slower league and easier for an offensive player to put up gaudy numbers.

Also, how would Kovalchuk respond to a lesser role? His entire life, he's been the best player - or one of the best - on every single team he's ever played on. He's a highly competitive, fiery player who always wants the puck on his stick. How would he perform if the offense didn't revolve around him, and he was only playing 15 or 16 minutes a night rather than 20-plus?

Boom: Legitimate top-six winger, power-play dynamo
Bust: Slow-footed, one-dimensional forward, defensive-zone liability

Carter Hutton

If you had to guess who led the NHL in both goals-against average and save percentage this past season, nobody would've thought Hutton. Yet, with sparkling marks of 2.09 and .931, the Blues netminder was indeed the league-leader in both.

Were these numbers a total outlier, or did he figure something out in his age-32 season? In his 106 career NHL games prior to this season, Hutton owned a 2.51 goals-against average and a .910 save percentage.

In all likelihood, Hutton's true form probably lies somewhere between his pre-2017-18 self and his surprising breakout season. Even if it happens to be closer to the latter, can he perform near that level with a full starter's workload? He only played in 32 games last year and his career high is just 40.

As the best unrestricted free-agent netminder available - and the only one with legitimate starter upside - Hutton will be highly sought-after, and will likely sign a contract that will reflect the thin goaltender market.

Boom: True No. 1 goalie
Bust: Above-average platoon/backup netminder

Riley Nash

Nash is in a similar situation to Hutton. He also just had a breakout season, but it came suspiciously late in his career at age 28. Was it a fluke? Or is he just a late bloomer? Coming into the 2017-18 season, his career high in points was 25, but he racked up 41 this past year with the Boston Bruins.

During Patrice Bergeron's 13-game absence in March, Nash filled in adequately, centering the team's top line and tallying 13 points. Was this a product of piggy-backing off Brad Marchand and David Pastrnak? Or proof that a player previously pegged as a "bottom-six guy" can actually produce when given a chance to play between talented wingers?

Even when Nash isn't contributing offensively, he's still helping his team, as he was the only player in the NHL with at least 50 takeaways but fewer than 15 giveaways this past season. As the third-best unrestricted free-agent center behind Tavares and Stastny, he's bound to get paid, but if he reverts back to his 25-point self, the contract will be a huge bust.

Boom: Defensively responsible second-line center who can produce offensively with right linemates
Bust: Offensively-challenged bottom-six center

Mike Green

Green will turn 33 on Oct. 12 and has a long injury history. Since the 2010-11 season, he's missed an average of 19 games, and underwent season-ending surgery on his cervical spine this year.

He's failed to top 36 points in three seasons since joining Detroit, but is the aging and lackluster Red Wings supporting cast to blame? Or has he declined to the point which his offense no longer makes up for his defensive-zone deficiencies?

Right-handed shooting defensemen are in demand in the NHL, so there will be no shortage of interest in Green. He can still effectively quarterback a power play, but whether a strong team around him can revive his 45-point potential remains to be seen.

Boom: 45-50 point D-man, prolific power-play quarterback
Bust: Extreme defensive liability, plateaus offensively

Michael Grabner

Since becoming a full-time NHLer in 2010-11, Grabner has been a productive, yet highly inconsistent goalscorer:

Grabner relies heavily on his blazing speed to create scoring chances for himself. He might get more breakaways than anyone in the NHL not named Connor McDavid. Outside of being a capable penalty killer, he doesn't offer much other than scoring. Playmaking isn't in his vocabulary.

He could be an affordable source of speed and goals for a team in need, but if he starts to lose that explosiveness (he turns 31 on Oct. 5), a multi-year deal could look bad in a hurry.

Boom: 30-goal scorer
Bust: 10-goal scorer

(Photos courtesy: Getty Images)

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