Porto and Shakthar will appear all out in their last match, because the results of the match will determine whether they will qualify for the last 16 or not. For Porto maybe a draw is enough to bring them to the knockout round, but still if they play it safe then the risk is also very large, because it is certain that Shakthar will appear all out. As for Shakhtar, victory is the only way they can get 1 ticket to the last 16.
The problem for them is that they will play as a guest team, and when their first meeting also lost to Porto, of course this will be even more difficult.