The Portuguese side stunned Juventus in the round of 16, and the Blues will be wary of the threat they possess.
Chelsea have looked solid defensively under their new manager, apart from the West Brom loss at the weekend, and comfortably beat Atletico Madrid in both legs to progress to the last eight.
Having won the competition in 2012, there will be hopes of a repeat this year, but to do so they'll have to get past Sergio Conceicao's dangerous side. Who will Tuchel trust with a starting berth?
In between the sticks it will be Edouard Mendy, who has established himself as the number one ahead of Kepa Arrizabalaga. The Senegal goalkeeper has impressed at Stamford Bridge and although he didn't have his best game against the Baggies, he won't lose his place.
The back three will likely change, however. Cesar Azpilicueta will start on the right side, but will be joined by Andreas Christensen and Antonio Rudiger, both of whom started the West Brom defeat on the bench.
Ben Chilwell may well come in for Marcos Alonso at left wing-back, and Reece James is likely to keep his place on the right, although there is a chance that Tuchel opts for Callum Hudson-Odoi there.
However, he hasn't done so in the league or Champions League since the 0-0 draw with Manchester United, so James is expected to start.
N'Golo Kante, unfortunately, picked up an injury whilst on France duty, and so will miss the game. That means that Jorginho and Mateo Kovacic will partner each other in the centre of midfield.
Mason Mount was omitted from the starting XI against West Brom having played in all three of England's games during the international break, and his energy was sorely missed. He did come off the bench and score, so expect to see him start against Porto.
Hakim Ziyech was the unlucky man to be dragged off following Thiago Silva's red card at the weekend, but Tuchel now appears to trust him, and with Christian Pulisic suffering a knock, the former Ajax man should be rewarded with a start.
Timo Werner has lacked confidence all season really, and with his form at an all-time low, and Porto likely to deploy a low block, he may miss out.
Kai Havertz has played as a number nine recently, but Olivier Giroud seems the more likely option, especially after his acrobatic effort in the last round against Atletico.
Tammy Abraham seems to have been frozen out by Tuchel, and is unlikely to make the squad.