No, they should not press the button and focus on Ligue and they never will. These games won't happen very often in their careers if they play for Lens and the fans would always want to see their players fight and not just give up no matter how hopeless the situation is. Look at Copenhagen and what they are doing due to the fights they put up and the help of their fans. It is amazing that a small team like that may qualify for the next round.
PSV has a difficult game away against Sevilla and then another difficult game against Arsenal at home. If Lens can beat Sevilla at home, there is still a chance that they make the miracle happen and everyone in that club wants it badly.
I know they are mediocre and these games are never decided in the underdog's favor with quality football, but with spirit and dedication. That is why teams like Copenhagen and Lens have a chance and yet they love to play in their domestic leagues.
edit: I have edited the missing words in the previous post.
And yeah, as I said, that doesn't mean they don't have to do their best in the Champions League competition. After all, as I said, like it or not, Lens has to play all his matches in various competitions. Let's flashback to when Lens started playing in two competitions, namely the Coupe de France. Their performance declined, although Haise was able to bring his team back to performing well.
Now we are talking about Copenhagen, let's refer to their ranking in their domestic competition, they are in first place with 33 points from their 15 matches. Their performance was inversely proportional in the Champions League, fortunately they faced United, a very unlucky team in that match. btw, Copenhagen is not in the same group as Lens in the Champions League group.
PSV is not much different from Copenhagen, they are in first place in their domestic league. In fact, PSV was unbeaten in 12 of their matches and swept all the matches with a win. unfortunately, their performance was not that good in the Champions League. Based on temporary odds, the Sevilla vs PSV match, the two teams seem to be evenly matched based on the bookie's odds. If PSV wins that means... Lens' chances of getting to the next round are quite tough. In fact, Lens will play an away match at Emritas, home of the Gunners.
Well, from what I have said, there is a gap between all the teams that I have mentioned here. both in the Domestic league and in the Champions League. the problem is, it's all up to the club, the coach and the players. If they insist on going all out, it means they will put in a big effort in these matches. every result can have an impact on their matches in domestic league competitions and Arsenal is no exception. So that's it, let's see what happens when the fifth matchday of the Champions League group phase is held.