Celtic forward Daizen Maeda faces six weeks out after suffering a knee injury in the challenge that earned him a red card against Atletico Madrid.
Maeda was sent off for a first-half tackle on Atletico’s Mario Hermoso after a VAR review upgraded his yellow card to red.
Celtic manager Brendan Rodgers said: “Daizen will probably be up to six weeks out with the injury from the challenge. He has strained his medial knee ligament.
“If he was in stronger in the challenge he probably wouldn’t have had the injury. The clash of feet has just opened up the knee ligament.
“It’s a big shame for us because he has been brilliant for me since I came here.”
Rodgers added to Sky Sports: “He’s a great reference for the intensity of the team so he’ll be a big miss for us.”
The Japan international has started every game except one this season, scoring twice.
The 26-year-old is set to miss Celtic’s next six Scottish Premiership games starting with Sunday’s home game against Aberdeen, which is live on Sky Sports.
Rodgers on poor CL campaign: ‘We haven’t felt inferior’
Maeda’s injury came in Tuesday’s 6-0 Champions League defeat at Atletico which leaves Celtic rooted to the bottom of Group E.
Celtic’s solitary point this season came against the Spanish side in Glasgow last month, but the Scottish Premiership champions remain winless in 14 Champions League games (D3 L11).
Rodgers told Sky Sports: “I don’t think in any game apart from that part of the game when we were down to 10 men that we’ve ever felt inferior in the game.
“I think what you do get at the Champions League level is the very highest quality, and situations that normally in your domestic league that seem like nothing turn into an opportunity for the opponents to score and most teams’ forward lines have got big quality. So that’s the main difference.
“It’s not about being pragmatic; we’ve been in every game we’ve played in – even with nine men against Feyenoord.
“It’s just a real challenge when you’re playing against top teams with 10 men, but it’s a learning and you have to move on.”
Asked whether the squad needs added quality if Celtic want to compete in the Champions League, Rodgers responded: “There’s absolutely no doubt.
“It’s what I’ve said all along that you need to have quality in your squad, in particular at the very highest level, that’s what wins you games and makes the difference.
“The players here deserve a huge amount of credit in terms of their performance in the games but of course in order to progress in it, it’s about quality and that’s the reality at this level.”