Jurgen Klopp said on Friday Liverpool goalkeeper Alisson Becker is on the road to recovery after suffering a calf injury, but it will "take some time" before he's available for selection.
The Brazil international had to be replaced during the opening Premier League game of the season, limping off after 39 minutes in the 4-1 victory over Norwich City on August 9 at Anfield.
New signing Adrian has deputised after arriving this summer on a free transfer, and the Spaniard has performed well so far.
Speaking ahead of Saturday's trip to Burnley, the Liverpool coach discussed Alisson's recovery and Adrian's recent first-team impact, per the club's official website:
"He [has] made steps, of course, but it was a proper injury, so it will still take time.
"How it always is with professional sportsmen, when you have a muscle thing and it takes long, then it takes a while as well until you can bring the muscle to at least the same level it was before.
"A calf muscle is pretty important for jumping—and for a goalie, it is quite important that you can jump from time to time, so it will take time.
"But, thank God—and hopefully it stays like this—we have a fit Adrian in the back and now in charge, which is good. So far, I am really happy with everything I saw.
"He is a good guy, which is important as well, but most importantly, of course, he can catch balls, and that’s good as well.
"The solution we found for it is really good, but of course, it would be better if Ali was around, but that will take still some time."
The arrival of Alisson and defender Virgil van Dijk over a six-month period in 2018 took Liverpool's defence to the next level. Klopp now has a world-class back line that is the envy of most teams.
Alisson's £66.8 million transfer from Roma last summer represented a world-record fee for a goalkeeper, and the success of winning last season's UEFA Champions League proved Klopp was right to recruit the stopper.
The Brazilian was named 2018-19 Champions League goalkeeper of the season on Thursday:
Adrian excelled during his time with West Ham United in the top-flight, and the 32-year-old has the required consistency of performance needed while Alisson work's his way back to fitness.
Liverpool have leaked goals in their opening games, conceding against Norwich, Chelsea, Southampton and Arsenal, but the Reds are the only team in the Premier League to maintain a perfect winning record in the opening weeks.