We don't really need to rest players on Saturday as we have a 5 day gap before we play Slavia and then no weekend fixture. The Celtic game is right before the international break, so no need to rest players. We then play cove on our first game back.
If we get past Slavia Prague, then we should definitely rest players before games. Given the game before the quarter final would be Cove Rangers, I assume that would be a given. I suspect we would rest players in the game between the 2 European games. We are at the end stages of a long and arduous season, players need a rest now and then.
If it meant going to the latter stages of the Europa League, I would happily throw away unbeaten in the league for that. I want us seeded in the champions league play off, getting to the latter stages of the Europa League should accomplish that.