Every NHL season there are a few surprises.

Whether it’s breakout players or those that suddenly fall into decline, often by the time the surface-level stats like point production or goal differential are about to go north or south, there’s a hint of what’s coming in the underlying numbers.

But it’s not like the underlying numbers never change, and changes there can be harder to predict. With that in mind, which players are the biggest surprises — positive or negative — by the underlying numbers this season?

The surprise: Bobrovsky has been awful in Florida

How it happened: The situation with Sergei Bobrovsky is two-fold. There looks to be a natural decline in his game — he’s gone from one of the most dominant goaltenders in the NHL in the high slot to just above average — and his drop in effectiveness in the inner slot is now two seasons at or below league average, while save percentage in that area league-wide is going up.

He’s still an above-average goalie from the high slot, which might make the overall numbers look better if he also wasn’t facing tougher shots from closer to the net this year than any of the previous three.

On top of all that, he’s also been unlucky on perimeter shots — where he has been remarkably consistent in previous years, posting numbers just a hair above league average.

Now he’s giving up weaker goals more often, while getting riddled with dangerous shots at the same time.

What it means: That gargantuan contract that the Florida Panthers signed Bobrovsky to last summer — paying him an average of $10 million per season until 2026 — isn’t looking so hot.

At 31 years old, Bobrovsky is far from done for — goalies can be erratic at the best of times, of course, and that only gets worse in their 30s — but the decline is concerning.

A bounceback season isn’t out of the question, either. And I wouldn’t be surprised if Bob has a few more good seasons to give, but he’s probably not going to be a top goalie under that structure, with that decline.

The surprise: Strome’s production has taken a hit, and it’s actually worse than it looks at the surface

How it happened: The Chicago Blackhawks have been a defensive mess for a few years now, so you probably shouldn’t hold it entirely against Dylan Strome that he owns the dubious honour of having the single worst on-ice differential in inner slot shots of all NHL forwards at 30.4 per cent.

But the bigger issue is — despite decent production — the Blackhawks don’t generate that much offence with him on the ice.

In fact, the 1.09 high-danger chances the Blackhawks get every 20 minutes with Strome on the ice at 5-vs-5 is the lowest mark of any Blackhawks forward.

As much as Strome’s 30 points in 40 games might give some comfort to the offensive struggles the Blackhawks experience when he’s on the ice, comparing him to the player he was last season makes it clear where things have fallen apart.

Strome’s shots from the inner slot have been halved, and while he’s still an above average playmaker, he’s gone from one of the league’s best at completing slot passes last year to just decent.

What it means: Strome was also among the worst players in the league in on-ice inner slot shot differential last year at 38.9 per cent, so a play driver is about the last thing I’d call him.

Still, he’s young enough and talented enough that I wouldn’t be too concerned about the lack of quality plays he’s creating this year. He may not be able to hit the point-per-game heights he did in his first season with the Blackhawks, but he’s still a very good offensive player, he just needs to be insulated.

The surprise: Teddy Blueger is actually awesome?

How it happened: The Pittsburgh Penguins keep finding diamonds in the rough to replenish their depth around their superstar players, and Theodor Blueger has taken a serious step forward this season, almost exclusively on the defensive end.

Partnered with another talented defensive player in Zach Aston-Reese, Blueger has seen improvement across the board after being pretty solid defensively last season as well, and the two of them have combined to be the Penguins’ most reliable defensive line.

Blueger isn’t the usual Mark Donk or Buzz Flibbet that the Penguins magically pull out of a hat to produce points at a crazy pace, he’s not a big-time scorer at the NHL level, but he defends exceptionally well.

What it means: Aston-Reese and Blueger combine to frustrate opponents and keep the bottom of the Penguins’ lineup well in the positives in driving play, which frees up their stars to run roughshod over weaker competition.

Winning the matchup game is something the Penguins are already able to do on most nights by virtue of having Sidney Crosby and Evgeni Malkin on the same team, but their depth allowed them to weather injuries to both players this season.

Now that both superstar centres are back in the lineup, the Penguins look incredibly scary as the playoffs get closer and closer.