A team can implode without 1 player if the team doesn't have any quality depth at that position. Compher is ok at 2C but not great. He's not a 1C that can go up against the other teams top defensive units and produce. After him they have nobody that can play 2C and produce. I like Veleno but a 2C he is not at all and the same goes for Ras, Copp, Fabbri and whoever else they can throw in that position even short term.
The defense is a shit show but if Seider got injured, the same would happen because they don't have anyone that can play RD worth a damn. Petry and Holl are garbage. Yzerman already needs to improve that position badly.
Lyon seems to have lost confidence or is overworked or both. That defense isn't doing him any favors either.
Players might have been expecting Yzerman to do something at the deadline to help them out especially with Larkin out but instead he just dumped Kostin for nothing and did nothing to upgrade the defense. I get not doing anything at center given Hertl was probably the only option for a top 6 center but i wouldn't want that contract and he is injured anyways so he wouldn't have been any help with Larkin out.
Defense is likely where Yzerman could have done something but instead he did nothing.
Wings are still in it despite their horrible streak of losing but they need to start winning again and for that, they need Larkin back, to play better defense and for Lyon or Reimer to find some confidence and play well. Being at home should help a bit with matchups with Lalonde being able to keep Petry and Chiarot away from the other teams top scoring lines and try to get Compher, Kane and Debrincat away from the the other teams top defensive units.