Sidelined after suffering a slight problem in training, the goalkeeper missed last month's 3-2 extra time defeat to Atletico at Anfield that ended the Reds' reign in Europe.
Adrian deputised in the Brazilian's absence, though the back-up was at fault for the first of two goals scored by Marcos Llorente that helped the LaLiga side seal a 4-2 aggregate triumph and a place in the quarter-finals.
That game was Liverpool's last outing before the season was halted due to the coronavirus pandemic, though Alisson - who had also sat out the 2-1 Premier League win over Bournemouth on March 7 - was nearing fitness before the break.
"He sent videos, doing some jumping and exercises,” goalkeeper coach John Achterberg told the club's website about Alisson's progress.
“Obviously, we were working with him until the lockdown and he was basically fit. Now it's for him to maintain it in the house, like the other goalkeepers.
"They all get their programmes from the fitness department so they will do the job and the work to try to stay as fit as they can, like all the other players as well."
Alisson and the rest of the squad are in a unique situation as they train at home due to social-distancing measures put in place to stop the spread of the virus.
However, the Premier League leaders have made sure all their keepers have the equipment required to remain sharp during the suspension, with no immediate sign of a return to action.
"If they needed boots, we got them boots; if they needed balls, we got them some balls. So at least they have the stuff to work in the house as much as they can," Achterberg explained.
"The physical department sent all the weights around that the boys wanted and needed, because some live in apartments and some didn't have all the equipment needed, so the club has provided that with Andreas [Kornmayer's] team.
"They put all together all exercises and some live training sessions. So we've all been in there to try to keep the banter going but also keep the fitness levels going."
The Brazilian went off in the 79th minute of Liverpool's 1-0 victory at Selhurst Park on Saturday and, according to widespread reports, is likely to be sidelined until at least the November international break.
Alisson was replaced by Premier League debutant Vitezslav Jaros against Palace as Caoimhin Kelleher missed that game through illness.
Kelleher deputised earlier in the season when Alisson was sidelined by a different hamstring injury, and is set to do so again, having recovered to join up with the Republic of Ireland national team.
Alisson also immediately pulled out of Brazil's squad for the upcoming World Cup qualifiers before having his scans.
"Alisson is our clear No. 1, the best goalkeeper in the world, so it's a blow when he gets injured for himself and the team," Slot said after the match on Saturday.
"We have a second option that's already good. Caoimhin has already shown that, which is why Caoimhin is the No. 2, and the last time Alisson was injured, I played Caoimhin."
The Reds have made a flying start to the season, winning nine of their 10 matches in all competitions.
However, they will likely have to navigate Premier League matches against Chelsea, Arsenal, Brighton, who they also face in the EFL Cup, and Aston Villa without their usual number one, as well as Champions League meetings with RB Leipzig and Bayer Leverkusen.
Diogo Jota scored the only goal nine minutes in after Eddie Nketiah had a goal disallowed in the first minute for offside.
Palace attempted to find a late equaliser, but amid their flurry of chances, Alisson went down after a routine clearance holding his right leg.
Having only just returned from a thigh injury, it is a worrying sign for the Brazilian, with big games against Chelsea and Arsenal coming up.
And though Slot was pleased to get the win that secured their stay at the top of the table over the international break, he confirmed it was unlikely Alisson would be available for their next games.
"Mostly for me, it's special [to be top of the table]," Slot told TNT Sports.
"Players go to their national team, and they think of the national team, but for me, if I lose it is three to four days of being unhappy. I think my wife will be happy as she will have someone home who is happy.
"Really satisfied with how we started the season. It is a good start, not only the results, but I liked our performance today.
"The fixtures are difficult, but I have felt how difficult Wolves and Palace are away. It is good that we have won these games, and it is up to us to show ourselves in the big games.
"Unfortunately, Alisson will not be with us in these matches with how he walked off the pitch."
Meanwhile, Oliver Glasner was left frustrated as he felt Palace should have had a penalty for a push by Virgil van Dijk on Marc Guehi.
They are winless in their first seven matches of the Premier League, their longest such run at the start of a campaign in the competition since 2017-18 (also seven games), but the German is not worried after seeing positive signs from his team.
"We should have had a clear penalty," Glasner said. "I disagree [with the PGMOL explanation] if it was on the halfway line they'd have given a foul. When it's a foul, it's a foul.
"It doesn't matter if it had an impact or not. If it is in the box, it is a penalty.
"It is frustrating we didn't get a point because we had chances. The way we played in the second half – creating more chances and moments and not giving them chances – gives me confidence."
The Portuguese forward netted after just nine minutes at Selhurst Park, darting in behind to pick out the bottom-left corner on his 100th start for the Reds in all competitions.
It could have been a different story though, as Eddie Nketiah had a goal ruled out for offside in the first minute, setting off too early before he dinked Alisson.
The Eagles pushed for a late equaliser but could not breach Liverpool's backline despite their late flurry of chances.
A sixth victory from seven matches moves Arne Slot's side four points clear at the top of the table before title rivals Arsenal and Manchester City play later on Saturday, while Palace remain without a win in 18th.
Data Debrief: Slot continues flying start
Liverpool have won all four of their away games under Slot so far, with the Dutchman just the fourth manager in Premier League history to manage the feat.
He is also the first Reds manager to win as many as nine of his first 10 games in charge (L1).
Palace showed some late fight, but it was not enough to flip the script and earn their first win of the Premier League season, with this their longest winless start since 2017-18.
Liverpool goalkeeper Alisson and full-back Trent Alexander-Arnold are also included, although there is no place for Mohamed Salah.
PSG's attacking trio of Lionel Messi, Neymar and Kylian Mbappe are among the forwards, as is Manchester United star Cristiano Ronaldo.
Veteran Dani Alves also won enough votes to make the list, even though the 38-year-old, who recently rejoined Barcelona, only played 16 times in domestic competition in Brazil this year.
Professional footballers across the world were asked to vote for the three players they considered to have the best seasons during the 2020-21 season among goalkeepers, defenders, midfielders and forwards.
FIFPRO said: "For the first time in 17 years, FIFPRO is updating the announcement about the most-voted players, reducing the shortlist from 55 to 23. This has been done to resemble a real-life 'squad' which, usually for international competitions, is the number of players involved.
"The three goalkeepers, six defenders, six midfielders and six forwards with the most votes earned a place in the 23-men World 11 'squad'. To complete this elite selection, the two remaining outfield players with the most votes were added."
The keeper, three defenders, three midfielders and three forwards with the most votes will be chosen for the World 11, with the remaining spot assigned to the outfield player with the next highest number of votes.
The final 11 will be announced at The Best FIFA Football Awards ceremony on January 17.
FIFA FIFPRO MEN'S WORLD 11 23-PLAYER SHORTLIST:
Goalkeepers:
Alisson (Liverpool, Brazil)
Gianluigi Donnarumma (Milan/Paris Saint-Germain, Italy)
Edouard Mendy (Chelsea, Senegal)
Defenders:
David Alaba (Bayern Munich/Real Madrid, Austria)
Jordi Alba (Barcelona, Spain)
Trent Alexander-Arnold (Liverpool, England)
Dani Alves (Sao Paulo/Barcelona, Brazil)
Leonardo Bonucci (Juventus, Italy)
Ruben Dias (Manchester City, Portugal)
Midfielders:
Sergio Busquets (Barcelona, Spain)
Kevin De Bruyne (Manchester City, Belgium)
Bruno Fernandes (Manchester United, Portugal)
Frenkie de Jong (Barcelona, The Netherlands)
Jorginho (Chelsea, Italy)
N'Golo Kante (Chelsea, France)
Forwards:
Karim Benzema (Real Madrid, France)
Cristiano Ronaldo (Juventus/Manchester United, Portugal)
Erling Haaland (Borussia Dortmund, Norway)
Robert Lewandowski (Bayern Munich, Poland)
Romelu Lukaku (Inter/Chelsea, Belgium)
Kylian Mbappe (Paris Saint-Germain, France)
Lionel Messi (Barcelona/Paris Saint-Germain, Argentina)
Neymar (Paris Saint-Germain, Brazil)
Players have had plenty of time to analyse their performances this season and we have previously used Opta data to examine some of the best attacking, passing and defending numbers from 2019-20.
Now it is the turn of the continent's top goalkeepers.
We have analysed five metrics for shot stoppers who have featured in at least 10 league games this season, thereby giving us a good summary of those who have led the way between the sticks.
The metrics include fewest goals conceded, best save percentage, fewest drops, the increasingly important passing accuracy and best keeper sweeper accuracy.
There are some familiar names, but also others you might not be expecting...
THE BEST GOALKEEPING STATS IN EUROPE'S TOP-FIVE LEAGUES 2019-20:
BUNDESLIGA:
Fewest goals conceded: Alexander Schwolow (20)
Best save percentage: Yann Sommer (74.58 per cent)
Fewest drops: Timo Horn, Lukas Hradecky and Manuel Neuer(all zero from 25 games)
Best passing accuracy: Manuel Neuer (87.69 per cent)
Best keeper sweeper accuracy: Timo Horn, Yann Sommer, Rafal Gikiewicz and Lukas Hradecky(all 100 per cent from 25 games)
LALIGA:
Fewest goals conceded: Ruben Martinez (14)
Best save percentage: Aitor Fernandez (75.61 per cent)
Fewest drops: Manolo Reina (zero in 26 games)
Best passing accuracy: Marc-Andre ter Stegen (85.55 per cent)
Best keeper sweeper accuracy: David Soria and Aitor Fernandez (both 100 per cent from 27 games)
LIGUE 1:
Fewest goals conceded: Runar Alex Runarsson (17)
Best save percentage: Predrag Rajkovic (79.07 per cent)
Fewest drops: Benoit Costil (zero in 28 games)
Best passing accuracy: Keylor Navas (84.55 per cent)
Best keeper sweeper accuracy: Benoit Costil, Mike Maignan, Regis Gurtner and Benjamin Lecomte (all 100 per cent from 28 games played)
PREMIER LEAGUE:
Fewest goals conceded: Adrian (10)
Best save percentage: Alisson (80.36 per cent)
Fewest drops: Martin Dubravka and Kasper Schmeichel (both zero in 29 games)
Best passing accuracy: Ederson (86.57 per cent)
Best keeper sweeper accuracy: Jordan Pickford, Rui Patricio, David de Gea and Mat Ryan (all 100 per cent from 29 games played)
SERIE A:
Fewest goals conceded: David Ospina (13)
Best save percentage: Wojciech Szczesny (79.76 per cent)
Fewest drops: Thomas Strakosha(zero in 26 games)
Best passing accuracy: David Ospina (87.07 per cent)
Best keeper sweeper accuracy: Bartlomiej Dragowski and Thomas Strakosha(both 100 per cent from 26 games)
AND THE TOP FIVE:
Fewest goals conceded: Adrian(10)
Best save percentage: Alisson (80.36 per cent)
Fewest drops: Martin Dubravka and Kasper Schmeichel (both zero in 29 games)
Best passing accuracy: Manuel Neuer (87.69 per cent)
Best keeper sweeper accuracy: Jordan Pickford, Rui Patricio, David de Gea and Mat Ryan (all 100 per cent from 29 games played)
