Liverpool have been handed a double boost with Trent Alexander-Arnold and Roberto Firmino both potentially being available for Saturday's fixture with Brentford.
Meanwhile, Firmino is yet to feature since before the international break after suffering a hamstring injury versus Chelsea.
Speaking to the club's official website, Klopp said: "Trent was not injured, Trent was a little bit ill. He's back in training, trained yesterday and will be fine.
"Bobby trained already for two or three days, so he is back in contention, let me say it like this. We used him a little bit as a 'joker' [in training].
"But he will be in the normal training and then we have to make a decision if we take him with us or not. Porto, 100%. Brentford, we have to see."
The Champions League fixture in Portugal takes place just three days after the visit to the Bees.