Lucas bravely attempted to continue playing but was clearly in great discomfort and eventually had to be stretchered off the pitch.
He is due to have his knee scanned on Thursday for a full damage report and Liverpool boss Kenny Dalglish has refused to comment on the issue until the full scale of the problem has been revealed. It has been reported that Lucas himself believes he could be out for a prolonged period of time.
While Lucas is no doctor and we will have to wait until the official scan results emerge to know fully the time period for his recovery, if he is to be out for a long period, it could well prove disastrous for the club.
Liverpool have been very impressive for the most part this season, and the last three games—two wins against Chelsea and an unlucky draw against league-leading Manchester City—have been some of the team's finest performances in recent memory. A lot of this can be attributed to Lucas. who has continued last season's outstanding form and who has been consistently solid.
Indeed, before his injury last night, he had turned in a performance of absolute class. His work rate, tackling and ball distribution were all top notch and he was really reveling in his role as the engine driving Liverpool's fast-breaking attack.
He has been Liverpool's best player again this year, the best holding midfielder in the Premier League and quite possibly the best in Europe so far this season.
It would be a great disappointment for Lucas, on a personal level, to be taken out of action at a time when his form is so exceptional and he is finally starting to receive the plaudits he deserves from a media that had long ago written him off as a poor player.
But more than this, Lucas' loss could be potentially disastrous for the remainder of Liverpool's season. If you were to look at Liverpool's starting XI, the reality—in my opinion, at least—is that of all the players on the park, the one who is the most irreplaceable at the moment is Lucas.
He has been in great form and he plays a position for which Liverpool—despite all the jokes made preseason about the depth of their midfield—have surprisingly scant cover.
Jay Spearing is the only man in the squad that could automatically step in and fill the role and, with no offense meant to Jay, it is very unlikely he would be able to do the job half as well as the league's leading tackler and a man whose pass completion rate is consistently over 85 percent and often over 90 percent.
Our next five league games are eminently winnable and, while I would feel a lot better about them with Lucas in the team, it is possible that we will be able to survive all right without him for the next few weeks.
After that, however, the going begins to get a lot tougher and our chances of success would depreciate greatly without our best player being available.
I think, as Liverpool fans, we ought first marvel at the progress this young man has made to go from vilified figure to possibly the most key member of the squad. And after we are finished marveling at his meteoric rise, we must cross our fingers and say our prayers and hope that the injury does not prove to be as bad as Lucas himself fears.
Our season could well depend upon it.