It's easy for Chelsea to play a team in other leagues than teams in EPL. I thought that Chelsea will start this season in a grand style and win three consecutive matches but they failed to win their first match. From the look at their performance yesterday, Maresca needs to work more on the team to stable their performance. Let it not be that they will be very strong in one match and become weak in three to four matches.
The reason is because the Premier League is a tough league for Chelsea to beat, and facing Premier League clubs can be even more challenging than facing clubs from other leagues. A concrete example of why Chelsea was able to beat PSG is quite clear. I've seen PSG not yet fully strengthen when facing top Premier League clubs. League 1 is still far below the standards of the Premier League, La Liga, Serie A, and the Bundesliga. So those who overestimate PSG as the strongest club in the world right now are likely mistaken.
Yes, Chelsea do need to focus more on the Premier League to face the competition. They've been in good form this season after winning the CWC. So, they can't afford to disappoint, and Chelsea fans will be hoping to can be better than last season.