The position of Lucas Leiva's deputy has been a position of concern for some time now. He's lacked a proper backup ever since Christian Poulsen left (and how quality of a backup he was is debatable), and it's become an especially problematic hole since his knee injury.
Bringing in a player who could properly spell Lucas in the middle would be valuable just for the ability to keep the Brazilian from tiring, which has been an issue since he returned to fitness after his devastating injury. It's also grown impossible to deny that Lucas has lost a step since then, making it harder for him to consistently display the imperious form that had become a fixture in the heart of Liverpool's midfield before he went down. As much as it hurts to say, bringing in someone that could potentially supplant Lucas down the road wouldn't be a bad idea either.
Yann M'Vila, 23, Rubin Kazan
Let's get this one out of the way first. The subject of near-constant rumors since he showed up at Anfield in November at the request of his friend Mamadou Sakho on a Rubin matchday, speculation is still high that M'Vila will be joining Liverpool next month. But... should he be?
M'Vila has significant physical talents. He's quick, strong, and is excellent in the air for a midfielder. Off the field, though, he's a mess. His attitude and behavior got him kicked out of the French national team, and then out of Stades Rennais and in to Russia instead of one of the European giants that he felt he had earned a place with.
It'd be one thing if he was performing well, but he's been resoundingly mediocre for much of his time with Rubin. He's done OK in the league, but he's been disappointing at best when facing better competition in Europe. While he fills a need positionally, it's tough to say that M'Vila is a fit for Liverpool unless you want to bank hard on him getting his head screwed on straight and realizing his potential instead of wasting it.
Fernando Reges, 26, FC Porto
The athletic Brazilian midfielder is an exciting potential addition to Liverpool's squad. With Porto in an apparent state of flux despite being joint-top in the Portuguese Primera Liga on points, it seems likelier by the day that they'll have a sell-off of some extent in January, and that Reges seems likely to be involved.
Reges is a steady presence in front of the defense. He reads passing lanes very well, and uses a good burst of acceleration to reposition himself to cut off passes and runs. He has enough physical strength to hang with the rougher play of the EPL, and can put in challenges both smart and hard when he needs to.
In possession, he's tidy with the ball. You won't see flashy dribbling or long diagonal balls over the top, but he doesn't do many stupid things with the ball to lose possession either. Reges is also always moving around, looking to make himself available as an outlet or as a linking player in a greater buildup around the box. He has a fair shot from outside the box as well, but I wouldn't generally consider it a strength.
Radja Nainggolan, 25, Cagliari
This would be a bit of a dream signing for me as I've long been an admirer of the Belgian, and there's been more and more rumors of late suggesting his potential availability. Inter Milan seems to be leading the pack for now, but he's talented enough to draw the attention of top clubs all over Europe.
Blessed with an ability to create from deep with accurate long balls both in the air and on the ground, Nainggolan is also a menace around the box, both with a strong right-footed shot and with his ability to put the ball at the feet of those in a position to do good with it. Saturday was a good example of that ability, as he picked out Davide Astori clear across the box and put it right on his left foot to serve to Nene, who put the ball in the net for the match's opening goal.
Nainggolan's real gifts, though, might be when the opposition squad has the ball. His work rate is incredible, and he puts it to use flying around the pitch to make as much a nuisance of himself as possible. He also has a gift for finding both passing and shooting lanes and getting his body in the way to end the attack. His ability to combine his defensive talents with his long passing to spring a quick counter would especially be of value with the way Brendan Rodgers has been embracing the counter over the past year.
Maxime Gonalons, 24, Olympique Lyon
If you want a pure defensive midfielder, Gonalons is your guy. Tall and powerful, Gonalons doesn't back down from a challenge and is a menace in the air. He doesn't add much in possession other than an outlet for recycling possession, but he also won't do much harm either, and can be an attribute on set pieces with his size and strength. He's been probably the best at his position in France over the past two seasons, and is ready for a greater challenge.
Napoli made an effort to get Gonalons over the summer and were rebuffed, but a brutal season for the one-time French power Lyon has left them reconsidering their stance on letting the midfielder go. The Italian side likely has the best shot at Gonalons' signature, but other sides will be in on the bidding as well.
Youssuf Mulumbu, 26, West Bromwich Albion
There's something to be said for experience in the EPL, and when a player with that experience has been a steady presence in front of West Brom's defense for four years, it's hard not to get interested. With the West Midlands side spiraling steadily towards the relegation zone, it's perfectly possible to see a player like Mulumbu coming available.
There's not much that's flashy or exciting about the Congolese midfielder, but in some ways that's a boon. He just quietly goes about his work and doesn't try to do much of anything above and beyond his abilities. He's effective in his role, though, and like so many quality holding mids, is under-appreciated for what he does simply because you don't notice him.