PSG is already showing some signs of weakness in them after they were humiliated by Chelsea in the CWC finals. PSG might not go as far as we expect them to go in UCL this season. However, they have always played in the semifinals for three consecutive seasons in recent of times. This season might be a different one for them, though, most of the big clubs are having little challenges in their performance.
After Chelsea defeated PSG in the Club World Cup final, and PSG failed to defeat Tottenham Hotspur in the Super Cup at full time, it shows that there's a dramatic decline in PSG's performance, and football fans shouldn't expect PSG to perform the way they did in the Champions League last season this season. PSG will start their Champions League campaign without their two key players, so I won't be surprised if PSG doesn't go far in this season's Champions League.
Exactly, the absence of their two key players would definitely affect their performance. That aside, the team have declined lin performance making it difficult for them to win their opponents easily. Enrique Luis might be cooking some thing deadly in the kitchen and I wouldn't underestimate his skills, because we might still see some surprises from them but not to the point of defending the title.