The ' bubble has been popped. After entering the NHL's expanded postseason format as the 23rd of 24 total seeds, the Blackhawks pulled off a rather stunning play-in round upset of the to secure their spot in the Round of 16. That landed them a matchup versus the top-seeded and, unfortunately for Chicago, things didn't go so well from there. Five games later and they're leaving the playoff bubble in Edmonton. So, where did things go wrong for Chicago? Let's take a look at some of the reasons why the Blackhawks are heading home. Getty Images An utter mismatch From the outset, this didn't look a series the Blackhawks were destined to win. Sometimes you can look at a team and recognize that, while they may not be as good as their opponent on paper, their strengths or style create a mismatch against a superior opponent. (Think the vs. in the play-in round.) That wasn't at all the case with the Blackhawks vs Marcus Morris Jersey . Golden Knights. Not only did Vegas look better on paper but their strengths (offensive zone po se sion and forechecking) were perfectly aligned to take advantage of Chicago's weak spots (lack of defensive zone structure and discipline). If things went the way we thought they would, it was going to be a quick series. And, as it turns out, they did... and it was. That brings us to... Patrick Beverley Jersey Inability to suppre s Golden Knights' attack The po se sion numbers in this series were overwhelmingly in Vegas' favor, which shouldn't really come as much of a surprise considering how well Vegas can cycle the puck and how unreliable Chicago's team defense can be. Let's take a quick look at the 5v5 numbers in the five games this series, : Shot attempts: 305 - 202, VGK Shots on net: 158 - 96, VGK High-danger chances: 62 - 32, VGK Expected goals: 13.4 - 6.9, VGK Goals: 13-8, VGK The Golden Knights did an excellent job of sustaining pre sure in the offensive zone and generating opportunities while keeping the Blackhawks on their heels at 5v5. was basically under siege this entire series and, honestly, it's a credit to him that things weren't a lot worse for Chicago on the scoreboard. Crawford stopped 172 of 187 shots (.920 save percentage) he faced in the series (at 5v5: 145 of 158, .918 save percent). The Toews line For the Blackhawks to have any chance in this series, they needed the top of their lineup -- including ' top line -- to have an unbelievable series. They weren't able to do enough, and Toews' unit had an especially rough go of things. The Blackhawks captain was able to get on the board with a goal in Game 5 but he had just two points in the series, as did . It's hard to pin a lot of blame on Toews individually when he played with two inexperienced wingers on the youngest team in the playoffs, but Chicago's top unit had a really difficult time matching up with Vegas' top forwards in this series. At 5v5, Toews' line had just 36 percent Amir Coffey Jersey of shot attempts and 33 percent of shots. That unit contributed one goal and were on the ice for five against. You're not going to win too many games when one of your top lines is run over to that extent. This leads us into... Coaching Simply put, it wasn't the best series from young Blackhawks coach Jeremy Colliton, especially when his team had its back against the wall. It was clear that adjustments needed to be made, especially to the top line, but Colliton made some questionable lineup decisions -- none more perplexing than inserting on Toews' wing in Game 5. Quenneville was a healthy scratch for the entire series leading up to Game 5 and suddenly he gets a slot on the top line in an elimination game? Uh, okay. Quenneville's presence did pretty much nothing for Chicago. Making matters worse, Colliton continued to play him even when it was apparent that it wasn't working. In 13:28 of 5v5 ice time, the Blackhawks were out-shot 3-10 and out-attempted 7-16 with Quenneville on the ice. By the way, that ice time includes Quenneville being trotted out with le s than three minutes remaining in the 3rd period while Chicago was down by one goal. Pretty inexcusable. Part of making adjustments is recognizing Mfiondu Kabengele Jersey when your adjustments aren't working, and Colliton seemed to show an alarming Shai Gilgeous-Alexander Jersey lack of response or urgency when it came to water filling the boat. Again, the defense It can't really be said enough... this Blackhawks team needs a defensive overhaul before they can truly be taken seriously. Just like it's hard to blame Toews for not being able to carry his line, it's hard to blame a 37-year-old for not being able to stand tall as the pillar of this defensive group. Keith averaged over 25 minutes of ice time in this series and things didn't go all that well for him. His lone contribution on the scoresheet was an a sist in Game 4 and he was a minus-6 in the series (on the ice for four goals for, 10 against at 5v5). Honestly, the Blackhawks put up a good fight but this group just wasn't good enough to withstand an elite team like Vegas, and the most glaring i sue is the defense. The onus is (and has been) on the front office to find more stability on the back end and, at this point, I'm not sure Stan Bowman is the guy for the job.