A cloud was hovering over Sidney Crosby this time last year.

The Pittsburgh Penguins captain had six goals and 13 assists for 19 points through the first 28 games of the 2015-16 season, an uncharacteristically slow start. Whispers circulated that his elite talent level was fading. Was he on the downswing of his career?

When the Penguins fired coach Mike Johnston and replaced him with Mike Sullivan on Dec. 12, 2015, they were ninth in the Eastern Conference.

And Crosby was reborn.

He kicked it down and finished the regular season with 36 goals and 49 assists for 85 points in 80 games -- which means he had 30 goals and 66 points in his final 52 games. He led the Penguins to a Stanley Cup, earning the Conn Smythe Trophy as playoff MVP. He celebrated briefly during the summer in Cole Harbour, Nova Scotia, before preparing to represent Team Canada at the World Cup of Hockey -- which he also won, earning tournament MVP honors as captain.

Two championships, two awards as the best player in those championships.

"Unparalleled," a Western Conference GM said of the accomplishment.

At the start of this season with the Penguins, he suffered a concussion and missed the first six games -- but he's still leading the league in goals. He has 21 goals and 13 assists for 34 points in 26 games. He had the most goals by an NHL player in his first 23 games in the last 20 seasons.

You could say he has silenced the critics and responded with one of the best calendar years by any pro athlete. And there are no signs of him slowing down.

"When he is skating and he's determined, you can't stop him," a Western Conference scout said.

He is the greatest hockey player in the world today.

"My whole time here, I drive home at night and say, 'I'm glad he's on our bench,'" Sullivan said. "I'm glad he's on our team, because he's one inspiring guy when he plays the game the right way. He's got a whole 'nother level. He's been dynamic."

Sidney Crosby kept his strong play rolling into the World Cup of Hockey. John E. Sokolowski-USA TODAY Sports

Crosby, 29, is smiling a lot these days. He wants to win it all again, and the Penguins are in the race for first place in the Metropolitan Division. He's not one to focus on the past, but he should be proud of what he's accomplished.

"It's been fun," Crosby said with a smile. "You work hard, and you hope to be in those situations and be rewarded. As a team, to win last year and then to be part of the World Cup and finish that off the way we did, yeah, it's fun when you win. There's not a lot of time when you think about that, necessarily, but looking back quick at it, it's been fun to be able to do that."

Humility is also one of his stronger qualities. When asked if he's playing the best hockey of his career, Crosby shied away from the notion.

"I don't know. I feel good," he said. "It's hard to compare, because certain things change. Ultimately, we won, and that's probably the biggest difference. There's still a lot of season left. You look at last year, the first few months, it can change pretty quickly, so you can't sit on anything. You've got to make sure you continue to improve."

Crosby is focused and committed to playing the game the right way. And his peers notice.

"He's the best player in the world, there's no question about that," said Boston Bruins forward Brad Marchand, who was Crosby's linemate during the World Cup.

When Crosby was injured, his teammates got a taste of what it's like to play against opposing teams' best players, which is something Crosby faces every game. It was further reinforcement to those around him -- and those watching from afar, too -- as to how focused and committed he is this season.

"What I always go back to is his work ethic," Sullivan said. "He is a tireless worker. He's the hardest-working player I have ever been around, and I've been around a lot of players. He, without a doubt, has the highest work ethic that I've seen. ... He's not as good as he is by accident. He's a very talented player, but his work ethic is tremendous. It's relentless."

Crosby is on an amazing run. His body of work and practice habits make him this good. And defensively, there's no reason Crosby shouldn't be considered for the Selke Trophy. His defense, which tends to go unnoticed, is just as good as his offense.

"Most elite players tend to lean towards the one-dimensional side," Sullivan said. "If you go through the league of superstars, the challenge for coaching staffs is to get those guys to be a little bit more committed away from the puck. I don't have that conversation with Sid."

During the 2016 Stanley Cup playoffs, he wasn't on the score sheet every game, but he was a beast every single night and had a huge impact on the team's ability to win. That's why he won the Conn Smythe.

"He's one of those guys that wants to be better, wants to improve his game, wants to be the best at all times, and that speaks volumes," said Bruins forward and Team Canada linemate Patrice Bergeron. "Last year, a lot of people were talking about him struggling. Then after Christmas he goes on a tear and brings his team to win a Stanley Cup. It's amazing to see. He's definitely the face of the league, and this year he's even more lethal. It's always a huge challenge to play him, and I can't say enough about Sid."

You could say Sidney Crosby had a very good year. EPA/MICHAEL REYNOLDS

So how does the best player in the world get better?

Simple: practice.

Crosby spends time before and after practice every day shooting as many as 80 extra pucks.

During the summer in Cole Harbour, he worked out with Bergeron, Marchand and the Colorado Avalanche's Nathan MacKinnon. Bergeron said Crosby is always thinking the game and trying to find ways to improve his game, both on and off the ice.

"He's a brilliant hockey mind," Bergeron said.

In the Cup finals against the San Jose Sharks, for example, he had winger Conor Sheary move so Crosby could win the draw back to defenseman Kris Letang, who was to pass to Sheary for the scoring chance. The play was completely drawn up on the fly, and it worked to perfection, largely because the Sharks hadn't seen it before.

When the World Cup began, Bruins coach Claude Julien, who served as an associate coach under Mike Babcock for Team Canada, learned firsthand what it's like to coach the best player in the world.

"It was pretty awesome," Julien said. "This time around, I saw him at his best. He's been one of the best players for a long, long time, but in my opinion, the fact that he's had some concussion issues has covered how good this guy is, because you didn't always see him at his best. And when he is healthy and at his best, you can see how dominant a player he is, and there's no doubt he's the best player in the world right now."

Julien is also quick to point out that Crosby seemingly doesn't have any weaknesses.

"He has everything you would want out of a player -- from the skill level, his shot, his vision, his skating, he's strong, creative and he's everything you would ever want in a player. I don't think he lacks anything right now," Julien said. "The thing that makes him great is his love for the game. He loves the game. He's not looking to cut corners. He loves coming to the rink. He loves being on the ice."

After winning his Cup, a weight seems to have been lifted off his shoulders. But you just know the fire still burns.

"I'm thrilled for him, and he's deserving of everything he's got," Sullivan said. "This kid's been on a whole 'nother level."