Nobody's perfect. Even the best teams in the NHL have some issues to work out, while the worst teams play a nightly game of whack-a-mole in an effort to address their many problems.
For this week's ESPN NHL Power Rankings -- voted on as always by ESPN's panel of experts -- we look at troubling trends for the league's 31 teams.
1. Nashville Predators
Previous ranking: 1
What's going on with the Nashville power play? The Preds are clicking at a 11.6 percent rate, worst in the NHL. They're not getting much production outside of the first unit, and players that have typically put up good power-play numbers (like Roman Josi) haven't gotten it going yet.
2. Tampa Bay Lightning
Previous ranking: 2
Mikhail Sergachev had 24 even-strength points in 79 games as a rookie last season. He has just three in 18 games this season.
3. Toronto Maple Leafs
Previous ranking: 3
The defensive pairing of Jake Gardiner and Nikita Zaitsev has had its problems, with a minus-37 in shot attempt differential and a minus-7.69 in relative goal differential rate.
4. Boston Bruins
Previous ranking: 6
Zdeno Chara's knee injury on Wednesday night didn't look good. The team was already without defensive stalwarts Charlie McAvoy (concussion), Kevan Miller (broken hand) and Brandon Carlo (lower body), as well as rookie Urho Vaakanainen, who suffered a concussion last month after being called up to fill in.
5. San Jose Sharks
Previous ranking: 5
Martin Jones has been a horror show at even strength during his first 14 starts of the season, with an .888 save percentage. The Sharks rank last in team save percentage at 5-on-5.
6. Minnesota Wild
Previous ranking: 10
In 13 of the Wild's 18 games, they've allowed the first goal. Silver lining: They've won eight of those games.
7. Winnipeg Jets
Previous ranking: 7
The Jets were fifth in the NHL in even-strength goals last season. In 2018-19, only the Coyotes (24) and Kings (21) had scored fewer goals at 5-on-5 than Winnipeg (27).
8. Washington Capitals
Previous ranking: 8
The Jay Beagle effect? The Capitals are at 48.7 percent on faceoffs this season, which would be the lowest percentage for Washington since 2014.
9. Columbus Blue Jackets
Previous ranking: 15
Riley Nash wasn't exactly acquired for his offensive acumen, but one could reasonably expect he'd have more than two assists in 18 games. And be a little bit better than a minus-39 in shot attempt differential at 5-on-5, to be honest.
10. Buffalo Sabres
Previous ranking: 20
Rasmus Ristolainen has nine points in 18 games, but defensively it hasn't been the best start: The Sabres are shifting him around the lineup, and every pairing ends up on the negative side of goal differential at 5-on-5.
11. Colorado Avalanche
Previous ranking: 4
Nikita Zadorov's ice time is down dramatically from last season, and he played just 7:22 on Wednesday night, benched after a penalty.
12. Calgary Flames
Previous ranking: 11
No team has trailed after two periods more than the Flames, who have entered the third period with a deficit 13 times. The good news is that they've won five of those games. Part of the issue: getting outscored 22-10 in the second period through 18 games.
13. Vancouver Canucks
Previous ranking: 12
Vancouver has some impressive offensive weapons, but they've outshot their opponents in only six of their first 20 games.
14. New York Islanders
Previous ranking: 13
It's an annual tradition in the NHL, commonly referred to as "Riding the PDO Train." The PDO is the sum of a team's shooting percentage and its save percentage. When it's too high -- like a team with a 104.76 PDO like the Islanders have -- it will regress to the mean (100) at some point. Fortunes change, luck runs out, and you just hope you've banked enough points beforehand.
15. Pittsburgh Penguins
Previous ranking: 9
What do Bryan Rust, Derick Brassard, Riley Sheahan and Matt Cullen have in common? They've scored one goal this season, as the Penguins' secondary scoring continues to struggle. Brassard, for what it's worth, has played only eight games due to injury.
16. Dallas Stars
Previous ranking: 16
Injuries, injuries and more injuries. Star defenseman John Klingberg is out for a month. Marc Methot and Stephen Johns have battled injuries. Connor Carrick is out. Devin Shore is out. Alexander Radulov is banged up. Martin Hanzal has yet to play a game.
17. Montreal Canadiens
Previous ranking: 14
The Canadiens have the league's ninth-best offense (3.22 goals per game) despite having the second-worst power play (13.0 percent success rate).
18. Carolina Hurricanes
Previous ranking: 21
The Hurricanes' penalty kill has been ... not good. It's No. 29 in the NHL (71.9 percent). That's 16 power-play goals against in 57 times short-handed.
19. Philadelphia Flyers
Previous ranking: 23
Shayne Gostisbehere has nine points in his first 18 games, down from his offensive pace from last season. Only four of those points are at even strength.
20. New York Rangers
Previous ranking: 24
In 18 games, the Rangers have led after the first period only twice, going 1-1 in those games. That speaks to another trend: With 11 first-period goals in 18 games, the Rangers are 30th in the NHL in that category.
21. Arizona Coyotes
Previous ranking: 19
The Coyotes' defense has been terrific, with 2.65 goals against per game, sixth best in the NHL. Unfortunately, their offense is also averaging 2.65 goals per game, good for 28th in the league.
22. Edmonton Oilers
Previous ranking: 18
Milan Lucic has one goal since March 5. At some point things go from being "trends" to being "a sad reality."
23. Anaheim Ducks
Previous ranking: 22
That the Ducks are this successful with a shot attempt differential of minus-237 through 19 games is quite a boost to John Gibson's Vezina Trophy case.
24. Florida Panthers
Previous ranking: 29
In 15 games, the Panthers are 3-3-1 in one-goal games. Which is fine, we guess, except for the part where a team averaging 3.20 goals per game has seen nearly half of its contests decided by one goal.
25. Detroit Red Wings
Previous ranking: 31
There was a time when the Red Wings were among the least penalized teams in the NHL. Not anymore: The Wings average 10:33 of penalty time per game, seventh in the NHL, and are a minus-21 in penalty differential at 5-on-5. Gentlemanly Pavel Datsyuk frowns upon thee.
26. Chicago Blackhawks
Previous ranking: 17
OK, so maybe Jonathan Toews won't end up winning that scoring title we all gave him after the first week of the season. He has five points in his last 13 games. He opened the campaign with 10 points in six games.
27. St. Louis Blues
Previous ranking: 27
Many noted this preseason that Jake Allen's play would make or break the season for his highly touted Blues squad. Through 12 games, it's broken it, with an .882 even-strength save percentage, ranking him 46th among NHL goalies. But hey, it's still early.
28. New Jersey Devils
Previous ranking: 25
Taylor Hall had 13 goals on the power play last season for the Devils in 76 games, leading the team. Through 16 games this season, he's yet to score one.
29. Vegas Golden Knights
Previous ranking: 26
Through 18 games, the Golden Knights have a minus-11 goal differential in the second period. They were a plus-21 in that frame last season. But the Knights overall have that feeling of being up huge at the blackjack table, sitting there for another hour, and then having the house put you in a financial hole. That's their season.
30. Ottawa Senators
Previous ranking: 28
Through 18 games, only one team was at less than 70 percent on the penalty kill. That team is the Senators, at 67.2 percent.
31. Los Angeles Kings
Previous ranking: 30
Really, there are a number of rotten trends to pick for one of the season's biggest disappointments, but we'll go with these stink bombs: The Kings have had a lead after the second period in only four of 17 games. They've trailed after the second period in 11 other games. They've lost all of those 11, in regulation. Ouch.