His manager David Moyes explained the decision to leave him out was tactical, as it enables the Reds to register the 18 year-old Belgian as an additional, available player from the third group game onwards. In the meantime, however, Januzaj will be ineligible to face Bayer Leverkusen tomorrow night and Shakhtar Donetsk away on Wednesday 2 October.
At Tuesday's pre-match press conference, Moyes said: "By 7 October, Adnan will have been at the club for the length of time that will allow him to go onto the 'B' list. It means he will become a youth player [for the Champions League].
"If we had put him onto the 'A' list now, then we would never have been able to class him as a youth-team player. So we needed to wait for two games to do that."
While Januzaj will miss the Leverkusen clash, Shinji Kagawa's chances of being involved have improved since Saturday when illness ruled him out of the Crystal Palace match in the Barclays Premier League.
"Shinji's better," said Moyes, "although he's still feeling symptoms in his throat. He's had a bit of flu as we said on Saturday. But he came in and did a bit of training yesterday and he's done a little bit today. So he's feeling a bit better."