its kind of win-win though isn't it?
if we win the game (or draw but still top the group) - hooray - we're on a roll! - momentum!
if we lose - never mind - weakened team - but now we are faves for the semis! clever old gareth!
Yes, a strange old situation and it will be weird watching the match with very few nerves. The only bad result as far as I can see would be a morale damaging drubbing by 3 goals or more.
In a strange way if both teams make a lot of changes it probably has more chance of making a game of it, what with players auditioning for the next game.