Roberto Firmino has flown to Barcelona with the rest of the Liverpool squad after training on Tuesday before their Champions League semi-final first leg.
The Brazil forward missed last Friday's Premier League defeat of Huddersfield with what manager Jurgen Klopp described as a "small muscle tear".
Midfielder Fabinho, who was not risked against Huddersfield after a blow to the head in the previous game, was also involved as the Reds held an open session at their Melwood training complex ahead of Wednesday's trip to the Nou Camp.
Their return to training comes as a major boost to Liverpool, who are aiming to reach their second consecutive Champions League final.
Klopp described Firmino's return to training as a 'major boost', but could not guarantee he would start at the Nou Camp, saying: "We all knew from the beginning it would be a race.
"We don't have to make a decision today because there's no game today, we can wait. It looked good so far but until tomorrow I have to make that decision - after lunchtime tomorrow. That's what I will do."
The manager did, however, confirm Fabinho's availability, explaining: "Every human being needs time and he needed that time, but it was already three or four days ago.
"If the Huddersfield game would have been a day later he could have played, but it was just impossible for that game. But it's OK."
Barcelona head into the tie having already secured the La Liga title with a 1-0 win over Levante.
Lionel Messi came off the bench to seal victory on Saturday with his 46th goal of the season, and Virgil van Dijk says Liverpool must find a way to stop the five-time Balon d'Or winner if they are to progress to the final.
"I think he is the best player in the world, I have said that before," said the Dutchman, who was recently crowned PFA Player of the Year.
"But you see how we play, how we defend, we don't defend one versus one, we defend all together and we attack all together as well - so we will see. We will be ready.
"The situation is that we are in the semi-final against Barcelona and we are going to face one of the best players... I think the best player in the world.
"But it is not only him, the whole team has a lot of quality and we will prepare well and that is what we are going to do.
"We have also a very good team so we can compete there as well so it is not like we are going there for a holiday or something."