The 2018-19 NHL season begins Wednesday. NHL.com is taking a look at the five keys, the inside scoop on roster questions, and the projected lines for all 31 teams. Today, the St. Louis Blues.

Coach: Mike Yeo (third season)

Last season: 44-32-6; fifth place Central Division

[RELATED: 2018-19 Season Preview coverage]

5 KEYS

1. Can Allen return to form?

Jake Allen was 27-25-3 with an NHL career-worst 2.75 goals-against average and .906 save percentage last season. After Jan. 1, the 28-year-old was 9-13-1 with a 2.99 GAA and .896 save percentage, which ranked last among 23 NHL goaltenders who played at least 25 games in that span.

The Blues are relying on Allen returning to the form he showed in 2015-16, when he had a .920 save percentage, and his six shutouts tied Ben Bishop and Martin Jones for second in the NHL behind Corey Crawford (seven).

Video: STL@COL: Allen robs Andrighetto with a glove save

2. Scoring outside top line

St. Louis was 24th with 223 goals (2.72 per game) last season, in large part because it didn't get much production outside of its top line of Brayden Schenn (70 points; 28 goals, 42 assists), Vladimir Tarasenko (66 points; 33 goals, 33 assists) and Jaden Schwartz (59 points; 24 goals, 35 assists), who were the only Blues with at least 55 points.

The additions of Ryan O'Reilly (61 points; 24 goals, 37 assists), David Perron (66 points; 16 goals, 50 assists) and Tyler Bozak (43 points; 11 goals, 32 assists) should help balance out the scoring.

Video: Tarasenko hopes to be ready for training camp

3. Improvement on power play

The Blues were 30th last season (15.4 percent) after finishing eighth (21.3 percent) in 2016-17.

Coach Mike Yeo said that the power play was filled with too many left-hand shots (Tarasenko, Schenn, Schwartz, Alexander Steen) and could benefit by incorporating Bozak and Perron, each right-hand shots. Bozak's 59 power-play points since 2014-15 were second on the Toronto Maple Leafs behind James van Riemsdyk (67). Perron had 18 power-play points for the Vegas Golden Knights last season after he had 13 with the Blues in 2016-17.

O'Reilly, who led the Buffalo Sabres in power-play goals (15) and time on ice (291:35) last season, gives St. Louis another center to use on either the first or second unit.

"Very few teams, I'll put it that way, have a group that can go out there and just play two minutes and be successful," Yeo said. "And I believe we have the depth and the quality of forwards now that we can put two solid power-play units together."

Video: Perron agrees to a four-year contract with St. Louis

4. Consistency

The Blues began last season 16-5-1 and led the NHL in points before going 7-10-1 in their next 17 games. From Feb. 11-March 8, they went 1-7-2, won eight of their next nine, then ended the season 1-4-1, which included a 5-2 loss to the Colorado Avalanche on the final day that eliminated them from Stanley Cup Playoff contention.

5. Youth movement

St. Louis is led by its core of Tarasenko, Schenn and Schwartz, but two intriguing prospects in forwards Robert Thomas and Jordan Kyrou could make an impact this season. Thomas, 19, was selected with the No. 20 pick in the 2017 NHL Draft, and had 75 points (24 goals, 51 assists) in 49 games with London and Hamilton of the Ontario Hockey League last season. Kyrou, 20, was a second-round pick (No. 35) in the 2016 NHL Draft, and was named OHL MVP after he had 109 points (39 goals, 70 assists) in 56 games with Sarnia.

Defenseman Jordan Schmaltz, 24, is another player who could see significant playing time with the Blues thin on defense. Carl Gunnarsson is recovering from surgery to repair a torn ACL on April 3 and Jay Bouwmeester (hip) has been a limited participant in training camp.

Video: Blues land at No. 8 in Prospect Pipeline

ROSTER RUNDOWN

Making the cut

The Blues are crowded at forward, but Kyrou could crack the opening-night lineup after he was close to making it last season. He has the speed and offensive skill to play in the NHL, and even if he begins the season with San Antonio of the American Hockey League, he will probably get a look at some point.

Most intriguing addition

O'Reilly is a two-way center who will help St. Louis on face-offs, where it was 12th (50.6 percent) last season. O'Reilly has won 58.3 percent of face-offs since 2015-16, second behind center Antoine Vermette, who won 59.2 percent of his draws for the Arizona Coyotes and Anaheim Ducks (minimum 1,000 taken).

Biggest potential surprise

Robby Fabbri was medically cleared this offseason following his second ACL surgery Sept. 28, 2017.

The 22-year-old forward has 66 points (29 goals, 37 assists) in 123 NHL games, but last played Feb. 4, 2017. He is day to day with a Grade 1 groin strain.

"I believe from looking at him that he knows just how important of a year this is for him and his career," Yeo said.

Video: PHI@STL: Fabbri bags second goal of the game in 3rd

Ready to break through

Thomas (6-foot, 188 pounds) missed development camp with an ankle injury but has three assists in four preseason games. Compared to Jonathan Toews and Patrice Bergeron, Thomas is expected to play in the season opener against the Winnipeg Jets at Enterprise Center on Oct. 4.

"I'm excited about Robert," Yeo said. "What I like, what coaches like, is he's got a well-rounded game. Robert's a guy who's going to learn quickly. He's a very coachable kid, he's a smart player, plays well on both ends of the ice. Another right shot, but a guy that's got a lot of elements, a lot of high hockey intelligence to his game."

PROJECTED LINEUP

David Perron -- Ryan O'Reilly -- Vladimir Tarasenko

Jaden Schwartz -- Brayden Schenn -- Alexander Steen

Robby Fabbri -- Robert Thomas -- Dmitrij Jaskin

Patrick Maroon -- Tyler Bozak -- Nikita Soshnikov

Joel Edmundson -- Alex Pietrangelo

Vince Dunn -- Colton Parayko

Jay Bouwmeester -- Robert Bortuzzo

Jake Allen

Chad Johnson