Lucas will undergo surgery, and his absence the rest of the season will loom large for Liverpool and manager Kenny Dalglish.
Now, without Lucas, Liverpool certainly face an even more uphill battle to secure a top-four finish and Champions League football for next season.
To think, just a few seasons ago, many Reds fans would not have been upset in the slightest at hearing Lucas would miss the rest of the season. Lucas overcame his many critics at Liverpool and has become a great holding midfielder for the Reds and offers great protection sitting just in front of the back four.
The midfield was already Liverpool's shallowest area on the pitch, so King Kenny certainly has his work cut out for him in finding a way to replace the Brazilian in the heart of Liverpool's midfield and ensuring the Reds stay competitive at the top of the Premier League table.
Jay Spearing is a born and bred Scouser and has been rising in the Liverpool first team for the last few years. The 23-year-old defensive midfielder has earned rave reviews from former manager Rafa Benitez and Kenny Dalglish each time he's been on the pitch for Liverpool.
Spearing impressed most recently in the 2-0 win over Chelsea at Stamford Bridge Tuesday night, which helped the Reds secure a semifinal spot in the competition.
Spearing has said himself he is disappointed at not featuring in the first team more this season. Well, here's his chance to prove he deserves it.
Last season, Spearing was a replacement to an injured Steven Gerrard and frequently impressed, so he will have to do the same this year, albeit with more pressure.
Gerrard, at 31, is battling injury regularly now, and this time around, Spearing will have to fill Lucas' boots instead of working alongside him.
The 19-year-old also impressed whenever he appeared in the Liverpool side last season, despite a six-week layoff due to his own knee injury.
Shelvey is much more of a scoring midfielder, but his presence can certainly make Lucas' absence all the more easy. Shelvey pushing forward would allow Jay Spearing and Charlie Adam to sit further back and offer more protection for the defense.
Because of his age and lack of Premier League experience, Shelvey will likely start out more as a substitute, but his pace and ability to keep the ball will offer comfort to Kenny Dalglish and Reds fans whenever he's on the pitch.
Dutch central midfielder Leroy Fer only joined FC Twente this past summer, and Liverpool had been thinking about about a summer transfer for the 21-year-old.
Now, Kenny Dalglish could speed up his plans in the wake of losing Lucas for the rest of the season.
Fer would offer Liverpool much-needed versatility as he can also play anywhere in the back line, another area that is not the deepest at Liverpool.
Fer has already scored five goals this season for Twente and has been marked as a future star for years. Playing for a team of Liverpool's stature could certainly enhance his rising status and the presence of international teammate Dirk Kuyt could help Dalglish woo him over fellow Premier League suitors Newcastle and Everton.
Eden Hazard is certainly not a like-for-like replacement for Lucas Leiva, but adding a player of his quality always helps your team, no matter what position you are lacking.
Lille has resigned themselves to losing the attacking midfielder at the latest next summer, and Liverpool may have a bargaining chip no other team can offer.
The on-loan Joe Cole is enjoying his time with the French side and wants to make the move permanent, and Lille shares the sentiment. Liverpool could use this in their talks to bring Hazard to Anfield.
The 20-year-old is one of the hottest young players in world football right now, and he would certainly be a fantastic investment for Liverpool future.
His pace and ball control would complement striker Luis Suarez very well, and his goal-scoring ability would take some of the pressure off Suarez as well.
Seydou Keita, like almost any player is the world would, struggles to see first-team action at Spanish giants Barcelona.
The midfielder recently said it was "fantastic" to be linked with a club like Liverpool, but that he would not make any decisions on his future until next summer.
However, with Liverpool's immediate need for a defensive midfielder, the 31-year-old could be persuaded.
He could offer Liverpool experience along with versatility and would be unlikely to cost Liverpool a lot of money or years.