With a home clash against Juventus to come on Matchday 6, the Cules hold their destiny in their own hands with regards to topping the group and getting what, in theory, should be a favourable draw in the round of 16.
"It's not usual for Messi to rest, I know this, but I have spoken to him about it even if decision is mine," Koeman explained in his pre-match press conference.
"Given the way the calendar is this season, there have been two moments when I could rest him, in Kiev and tomorrow.
"We are already qualified and this way I am able to give opportunities to others. We need to win Saturday's match in LaLiga, so this is the right time for him to rest. After tomorrow there won't be any other chances to do that."