As Mateo Kovacic hobbled off the Stamford Bridge pitch it was impossible not to think of the implications for Sunday's Carabao Cup final against Liverpool.
The Croatian midfielder has been Chelsea's standout player this season and to see him substituted just six minutes into the second period against Lille was certainly concerning. Particularly given the role Kovacic played in the previous game against Jurgen Klopp's men.
Thomas Tuchel did not seem so much concerned about the severity of the injury as much as the tactical implication of delaying the move, which is partly reassuring.
He told BT Sport: "I don't know. I should have substituted Kova at half-time so we could have saved one more change. I did not speak to the doctor yet with Hakim, I hope it is not too much.
"It is the story of the season, we do substitutes because of injuries. Today is Tuesday, there are a lot of days to recover until Sunday.
"We will take care to be ready on Sunday. We don't like that much injuries and would like impact from the bench in a tactical manner, we hope the guys will be ready for Sunday."
However, to see Ruben Loftus-Cheek enter the field was an illuminating moment.
The midfielder only returned from an Achilles issue against Crystal Palace at the weekend with a 15 minute outing. Before that the academy product had only featured for 25 minutes across the League Cup semi-final legs with Spurs and 45 minutes against Chesterfield in January since his last Premier League minutes in early December.
However, his cameo against the French champions belied that fact.
Despite a rash yellow card, the former Fulham loanee settled into the base of Chelsea's midfield produced his trademark dribbles, only completing fewer than Christian Pulisic and Marcos Alonso, and helped control the game with his passing too, maintaining the best completion rate in the Chelsea side.
It was interesting to see Loftus-Cheek as the man turned to given the prestige Kovacic, N'Golo Kante and Jorginho have earned this season and beyond. Perhaps after losing the former, Tuchel simply did not want to risk Jorginho from the bench ahead of Sunday's final.
That said, with his dribbling ability, the 26-year-old provides a profile more akin to Kovacic and with the Champions League tie still delicately in the balance at 1-0 at the time he entered the fray, there was still plenty important to play for.
It is easy to forget the extent of Loftus-Cheek's role this season, given he entered the term in a similar position to Ross Barkley with many uncertain of the role he could take up following a difficult loan at Craven Cottage.
The England international has already made 22 appearances despite missing a number of matches through injury and Covid-19.
Though he was unable to make the trip to Abu Dhabi for the Club World Cup, Tuchel wasted little time in seeing him return to action against Palace. Where the likes of Barkley did not make either of the German's last two squads, and Harvey Vale did, Loftus-Cheek had an important contribution to make.
There is plenty of talk about the midfielders are interested in buying this summer in Declan Rice and Aurelian Tchouameni. There is even plenty of hype around the returns of the likes of Conor Gallagher and Billy Gilmour.
However, Loftus-Cheek's role could still prove influential as Tuchel once again showed his willingness to trust him on an important occasision. The German coach served an important reminder to everyone at Stamford Bridge.
