The Brazilian duo have missed training so far this week, with Lucas likely to return in Friday’s session and Firmino potentially involved on Saturday.
“We spoke about Roberto. Since a few weeks [ago] we have to manage the intensity in training,” Jürgen Klopp explained at his pre-match press conference.
“It’s a little bit another muscle which he feels. Everybody can imagine, Roberto is a real mentality player, so he wants always [to play]. We need to make the decisions for him sometimes.
“We left him out of training. It’s a muscle thing. We have to wait and give him as much time as possible.
“Lucas, after the game, [felt the same]. I asked both a lot of times, ‘OK? OK?’ and everybody said ‘Yes, yes’. After the game they felt it.
“After the game, Lucas felt two different muscles and we said ‘OK, we have to wait also’. Lucas could be back in training today, we have to see. Roberto, tomorrow if possible. Then we make the decisions.”
Free clip: Jürgen's LFC injury update
On a more positive note, Klopp will have Adam Lallana and Daniel Sturridge as possible options for his starting XI at the London Stadium – after another week of training for the returning attackers.
The manager added: “After Watford, when Adam came in early, he felt the 70 minutes really. We had to manage the intensity through the week.
“After coming from injury, if you could immediately play 90 minutes that would be perfect. But, unfortunately in football, the real match is too intense that you can work that hard in training.
“He trained only twice before this game [against Southampton last weekend]. He was an option, but actually not for starting. Now he is in another situation, so that means we have two more options, if nothing else happens.
“I’ve said it a few times, as long as we have 11, we will fight.”