Every club's 25-man list was submitted to Uefa at the start of September but Benfica coach Jorge Jesus will have one player taking his first steps in this season's competition when Celtic visit the Stadium of Light on Tuesday, and the timing could not be better.
Anderson Luis da Silva, better known as Luisao, will be back in a Benfica shirt. Until now, the Portuguese side have been deprived of their talismanic captain for the Group G campaign, but his return to boost their bid to finish second behind Barcelona could be crucial in the penultimate round of games.
The towering Brazilian centre-back has been on the sidelines serving a two-month suspension for pushing a German referee during a pre-season friendly against Fortuna Dusseldorf. Luisao was protesting at the expulsion of his erstwhile colleague, Javi Garcia (now at Manchester City), but referee Oliver Fink abandoned the game and threatened to sue the player.
Uefa and Fifa then endorsed the Portuguese FA's ban on Da Silva. He was also suspended from Champions League games and, although he flew to Glasgow with the Benfica squad for the opening night in September, he sat in the stand at Celtic Park as the sides drew 0-0.
Luisao acknowledges that missing 11 games and only training for the last eight weeks will have left some rough edges in his play, but the fact that Jesus put the 31-year-old straight into the side for the Portuguese Cup tie at Moreirense on Friday night illustrates how keen the Benfica coach is to have Luisao back. His appearance against Celtic is a certainty.
"It is like a new signing for Benfica," admitted Mitchell van der Gaag, the former Motherwell central defender who has played and coached in Portugal for the last 11 years. Van der Gaag was playing for Maritimo when he first came up against a raw, young Luisao (who has been at Benfica since 2003), but he had moved on to become manager by the time the Brazilian had his best season, inspiring Benfica to their last Portuguese title in 2009-10.
"Luisao is the leader of the team so, in my opinion, he will play against Celtic," said Van der Gaag. "All he has done for the last two months is train so he needed the game against Moreirense. For Benfica, it's a big boost that he is available again. Their defence is much better with him in it but he's also a strong personality in the dressing room that other players respect and give a bit extra for.
"I played against him a few times and he is difficult to contain when he's in your box. He is so tall and gets on the end of corners. He scores with plenty of headers and he has a good record in Europe against British teams. He scored when Liverpool lost at the Stadium of Light, when Benfica knocked them out, so Celtic will have to watch him closely."
Liverpool's eclipse came in 2005-06, as Benfica reached the Champions League quarter-finals. Last season, the Eagles clipped Manchester United's wings, again en route to the last eight, where they lost to Chelsea.
"Benfica like playing against British teams, it suits their counter-attacking style," said Van der Gaag, who is now coach at another Lisbon club, Belenenses, while his son, Jordan, is in Benfica's famous youth system.
Luisao offers a huge contrast for Celtic after two games with Barcelona in which they were able to exploit the lack of inches in the opposition defence. It will be harder for Georgios Samaras to win the same number of aerial contests in the Stadium of Light.
However, that 6ft 4in frame comes with some flaws. Luisao's use of the ball means he is not everyone's cup of tea and, while he has won 43 caps for Brazil, he was taken to the 2006 and 2010 World Cup finals but did not kick a ball under Carlos Alberto Parreira or Carlos Dunga.
Yet, Luisao revealed last week that it was support from back home which helped him get through his two months' punishment. "It is very hard when you are deprived of doing what we are born for," the Benfica captain said. "All the support I received from Brazil, my family and the people who follow my career was important.
"I'm used to being out on the pitch and helping. It really hurt not being able to contribute but this was a step that strengthened me and I will come back stronger. I feel butterflies in my stomach after a long time without playing. I know I may have some difficulties in the beginning, but I have enough experience to know how to deal with it."
Luisao's return will mean another Brazilian defender, Jardel, who played against Celtic in Glasgow, will be back on the bench. Jardel was bought to replace David Luiz when the latter joined Chelsea, but slipped so far down the ladder that Jesus sent him for a spell with the reserves – Benfica B – to play in the second division against Van der Gaag's Belenenses.
"The game was played at the Stadium of Light," Van der Gaag said. "There were only 3000 spectators there but my players were taking photos before the game for their Facebook pages. They froze. It was my mistake and I will not let them do that again."
Celtic will be just as keen to avoid being starstruck tourists on Tuesday night.