Atletico Madrid coach Diego Simeone (AFP)
Defeat would see Atletico miss out on the knockout stage for only the second time during Simeone's near decade-long tenure.
Atletico and AC Milan both trail second-placed Porto by a point.
Milan host Liverpool, who have already qualified as Group B winners, and are above Atletico on goal difference.
Should both Atletico and Milan win their games it will come down to goal difference as they are tied on their head-to-head record.
There have been clear signs this season of decline in the Atletico side Simeone has taken to two La Liga titles and within a whisker of two Champions League triumphs.
Atletico go into the match in Portugal on the back of a home defeat in La Liga, a 2-1 loss to Mallorca on Saturday.
However, Simeone is adamant the players will deliver for him and the fans.
"I have full confidence in my team," said Simeone at his press conference on Monday.
"We have worked on the things we needed to and now what we have to do is to talk amongst ourselves so that we feel at ease on the pitch.
"The one thing that is important to me is that we feel good on the pitch, which will allow us to control the game and chances will flow from that."
The combative former Argentinian midfielder said he is not underestimating the challenge that faces his side.
"We have a very important match against a very good side, who top their league," said the 51-year-old.
"Porto are a team who I like a lot and who go into the last round favourites because they have more points than either ourselves or Milan."
Atletico's Spanish international midfielder Marcos Llorente said the team were used to facing tight situations like the one confronting them.
"This team has the character and personality to get out of this," he said.
"We have done it before and this situation is no different.
"These are the sort of matches every footballer enjoys playing."
Simeone said Uruguayan central defender Jose Maria Gimenez will miss the game through injury, but Belgian international Yannick Carrasco is once again available for selection.
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