Well it's true Jurgen was to blame for the poor performance of his boys but I guess he had settled within himself that in life you lose some and win some. Imagine this were the Premier league I doubt he'd do that because there will be a lot riding on his decision. Let's say he had to sub his best players to bring on the average ones so he can at least rest them for the game in front with Brighton as I regard that game more important than this one they played against Man UTD.
Right now, Liverpool are second place with 64 points but the Gunners have the advantage over them with goal difference and I don't think they will joke with the game by letting the opposition take advantage because that would mean a drop in points and I doubt they may be able to come back if that should ever happen.
There are difference level between Premier League and FA Cup, some teams used their second players composition or giving opportunity for the academy players to get more minutes playing in FA Cup. I don't think problem with Liverpool after eliminating from FA Cup and they will focus the most target by winning Premier League and UEFA Europe League. Current standings, Liverpool left goals productivities from Arsenal and its not huge problem with Arsenal and Manchester City will face each other after international matches break out. The draw result will be more advantage for Liverpool if can win next match against Sheffield United.
Regarding with teams opponent face by Liverpool in matches left, all teams have the same opportunity for winning premier league tittle with Liverpool has match left against Arsenal and the crucial match will Arsenal keep in consistency performance against with top fourth standings teams.