Five reasons the Blackhawks were eliminated

The warning signs were noticeable all season.
The Chicago Blackhawks stayed among the NHL elite by finishing with 103 points during the regular season but couldn't patch all the holes left behind from a tumultuous offseason roster shakeup. In the end, that's ultimately what led to the defending Stanley Cup champions' repeat bid ending in the Western Conference First Round.
Compared to the past few seasons, the Blackhawks had the puck a lot less this season, gave up more scoring chances because of it and learned to win by strategic counterattacks. It put a lot of pressure on goalie Corey Crawford, but he was up to the task until a late-season upper-body injury kept him out almost a month.

In the playoffs, the Blackhawks' best-of-7 series against the St. Louis Blues was a classic. It lasted seven games after Chicago fought back from trailing 3-1 but ended with the defending champions ousted in the first round for the first time since 2012.
Chicago has elite talent, but each offseason keeps chipping away at the core group that won the Cup three times in six seasons. The Blackhawks get thinner every season and this time they were just too thin to get past the Blues.
Here are five reasons the Blackhawks were eliminated:
1. Defensive depth:Chicago lost a lot of talented forwards from its 2015 Stanley Cup-winning roster, but the departure of defenseman Johnny Oduya was the most damaging.
Oduya, a veteran who formed a shutdown pairing with Niklas Hjalmarsson for three-plus seasons, signed with the Dallas Stars as a free agent on July 15 and left a big void in the Blackhawks' top-two defensive pairings.

Three young defensemen rotated into the role, playing with Brent Seabrook, but the issue was never resolved. It didn't help that veterans Trevor Daley, Rob Scuderi and Christian Ehrhoff didn't pan out.
One of the rookies, Erik Gustafsson, played a key role in the Blues' game-winning goal in Game 7. The series wasn't lost on just that play, but it was a glaring example of Chicago's biggest challenge this season.
2. No finish:Patrick Kane and Jonathan Toews combined for one goal against the Blues. The Blackhawks' other top-six players eventually got it going offensively, but Kane and Toews never did.
Kane scored the game-winner in double overtime in Game 5 but otherwise was stymied by St. Louis goalie Brian Elliott. Toews had six assists but was held without a goal for the first time in his postseason career.
Teuvo Teravainen was limited to one assist in seven games a year after having four goals and six assists in 18 games to help Chicago win the Cup. Like the regular season, he didn't have the kind of impact the Blackhawks hoped he would.

3. Brian Elliott: The Blue goalie started all seven games and played well, despite hiccups in Games 5 and 6. Elliott had a 2.40 goals-against average and made 236 saves on 254 shots for a .929 save percentage.
Elliott made several clutch saves to keep Kane from scoring, made his share of highlight-reel saves, and was technically sound most of the series.
4. Discipline:From Duncan Keith's high-sticking incident against the Minnesota Wild on March 29 during the regular season to Andrew Shaw's untimely penalty and antics at the end of Game 4 to Gustafsson's role in the winning goal of Game 7, the Blackhawks didn't do themselves many favors.
Keith missed Game 1 while serving a six-game suspension and the Blackhawks lost 1-0 in overtime. The defenseman had three goals, two assists and played 31:27 per game in the next six games. The one game he didn't play might take some time to forget.
Likewise, Shaw's late penalty that preceded his suspension for using a homophobic slur basically ended Chicago's chance to send that game to overtime. In such a close series, those factors loom large.
5. Balancing act: Coach Joel Quenneville searched high and low all season to find a solid, balanced group of forward lines he could roll in succession without worrying about chasing matchups.

He finally stumbled onto the right combination, but it wasn't until Game 5 of the series. By that point, the Blackhawks were already down 3-1. Quenneville's decision to put Kane and Toews on the top line, a move he saves for desperate situations, keyed the whole thing.
The biggest benefit was the creation of a dynamic third line with Andrew Ladd and Marian Hossa flanking defensive center Marcus Kruger. The combination helped spark Hossa, who looked years younger in the final three games.
It just happened a little too late in the series.