Liverpool issued an Alexander Isak fitness update after the striker was absent from the squad for his new club's 1-0 victory against Burnley.
The Sweden forward hadn't taken part in any collective training sessions with Newcastle this summer following Eddie Howe's revelation that the star had "gone on strike" by refusing to feature in any of Newcastle's pre-season fixtures.
A Liverpool statement on their club website read: "Liverpool are aiming for Alexander Isak to be ready to make his debut when they host Atletico Madrid on Wednesday night. The Sweden international, a deadline-day arrival at the Reds, has trained alongside his new teammates at the club this week.
"He was not, though, named in the matchday squad by Arne Slot for Sunday's resumption of Premier League action away at Burnley.
"Slot was asked about Isak's fitness progress ahead of kick-off at Turf Moor and revealed the Champions League tie in midweek is the target for the No 9 to first feature."
Slot had said to Sky Sports: "As everybody knew, he didn't have any team training at Newcastle, then went to the national team [and] only played there for 15 to 20 minutes.
"We think, with a week where we play three games in seven days, this is the best lead-up for him to be available against Atletico Madrid.
"That's always difficult to say [how quickly he will be] up to full speed. What I can say is that normally in a pre-season, after one or two weeks you play your first 45 to 60 minutes, you build that up gradually."
In his press conference, Slot explained: "So, I can explain to you – it will take a few minutes but is not that difficult to understand.
"So, if you start the season when the players who have been off for three or four or five weeks, you give them a certain base. You give them a lot of good sessions before they are able in the end of the week to play 45 minutes.
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"We got him from Newcastle in a state where you could say his pre-season is going to start now, so then he needs proper minutes of training before he has a certain base, let alone for him to play twice in three days.
"So, that's what we do, what we try to prepare players for in the beginning of the season is [to play] once a week and then we try to do more and more and more for a minimum of two games a week so they are ready for that schedule.
"Now, Alex is far from ready for that schedule of three games in a week, 90 minutes.
"But then we could use him today for five minutes and then Wednesday again 10, and then 15, but we don't believe that is the way to build him up.
"We believe it's the way... Sweden did the right thing of giving him good sessions without playing him a lot because if you play the player you cannot give him good sessions.
"They did the right thing [and] we did the same, so now he will be able either Wednesday or Saturday to play 45 as a minimum, and maybe a little bit more.
"But if he plays 45 on Wednesday don't expect him to play 45 or more on Saturday because his body is not prepared for that, in our opinion."
Isak's fitness status will be no surprise to Newcastle staff who did not expect him to be close to full fitness until October.