3 players Juventus should try to sign in January transfer window

Despite sitting comfortably atop Serie A heading into 2017 - and winning its Champions League group, too - it hasn't all been smooth sailing for Juventus this season.

The performances have often been laborious and frustrating, and while injuries have certainly played their part, manager Massimiliano Allegri has yet to find a formula that gets this star-studded machine consistently firing on all cylinders.

The January transfer window provides a brief opportunity to add the missing ingredient for a side with aspirations of capturing all three trophies on offer.

Here are three players Juventus should look to sign over the next month:

Steven N'Zonzi (Sevilla)

The club brass knows it, Allegri knows it, and it's clear to see for supporters and pundits alike: Juventus has problems in midfield that need addressing in January.

The departure of Paul Pogba left a glaring hole - as was expected - and the arrival of Miralem Pjanic, while important in replacing the Frenchman's creativity, hasn't entirely filled the gap. That's not a knock on Pjanic, either; replacing everything that Pogba brings to the table is impossible for one man. There's a reason he's the most expensive player in history.

Related: Juventus captures Rincon from Genoa for €8M plus add-ons

Axel Witsel was the man tabbed to help soften the blow of Pogba's return to Manchester United this past summer, but the deal fell apart on the final day of the window after Zenit St. Petersburg pulled the plug. Naturally, Beppe Marotta kept knocking on the Russian side's door, and was operating from a position of strength: Witsel's contract expires in 2017, and Zenit risked losing him for free if a January deal wasn't brokered.

Turns out it was all too simple, too good to be true.

The afro-clad Belgian is on his way to China, admitting earlier this week that he received an "irresistible" offer from Tianjin Quanjian. He'll reportedly earn a monstrous annual salary of €18 million, quadrupling the reported yearly wage he was being offered by the Bianconeri.

Marotta now needs to look elsewhere, and he should cast his gaze to Andalusia, where Steven N'Zonzi has been running the show for Sevilla. The angular Frenchman, 28, is enjoying the best year of his career, his calm, composed ball retention skills and lanky athleticism making him a force for manager Jorge Sampaoli.

N'Zonzi's potential addition wouldn't be a world-altering move that immediately solves all the club's problems, but he's a marked improvement on Stefano Sturaro, who has been playing alongside Pjanic, Claudio Marchisio, and Sami Khedira of late. Indefatigable as the young Italian is, his limited skill on the ball is a problem, particularly when Juventus is pressed high by the opposition; Sturaro simply isn't skilled enough to be an effective outlet when the defence is faced with high pressure.

N'Zonzi is.

Despite a hefty release clause that reportedly stands at €30 million, Marotta needs to pounce, lest Juve continue to labour and throw away what could be a historic season.

Pol Lirola (Sassuolo)

While the predominant issue plaguing the Bianconeri this season has been the inability to strike the right balance in central midfield, the conundrum at right-back has been equally problematic. In the wake of Dani Alves' broken leg suffered in late November, manager Massimiliano Allegri has had no choice but to opt for the ineffectual Stephan Lichtsteiner.

An important contributor in the trophy-laden run of recent years, the Swiss has been nothing short of woeful in 11 Serie A appearances this season, consistently finding himself out of position and leaving his fellow defenders vulnerable; his porousness has been made ever clearer considering opposite number Alex Sandro has been a monster down the left flank.

With Alves out and Lichtsteiner on the decline, reports have suggested Juventus could recall 19-year-old Pol Lirola from his loan spell at Sassuolo. Though still raw, the Spaniard, who has made 18 appearances in all competitions this season, is a bright attacking right-back who has shown flashes of why he's viewed so highly in Turin.

His current deal is slated to see him remain with the Neroverde until 2018, but Juventus would be wise to cut that short and throw him into the fire. Frankly, he can't be any worse than the incumbent Lichtsteiner.

Mattia Caldara (Atalanta)

The two potential deals outlined above would address the squad's immediate issues, but here's one with an eye to the future.

Reports suggest Marotta has already secured the signing of young Italian defender Mattia Caldara from Atalanta, a move that would, in theory, solidify Juventus' backline in the long-term.

Related - Report: Juventus swings €20M deal for Atalanta's Caldara

Giorgio Chiellini, though enjoying a recent renaissance after returning to the side, is increasingly injury prone as he continues to age; Andrea Barzagli is 35 years old; Leonardo Bonucci will be 30 in May. Fantastic as the vaunted "BBC" backline has been over the years, it's time to start planning for the years to come.

With Daniele Rugani already in place, getting the ink to dry on this deal would give the Old Lady a stable of Italy's best central defenders - something the club has a track record of doing.

Though not as polished in possession as Rugani, the 22-year-old Caldara has been an unflappable rock for Atalanta this season. More Barzagli than Chiellini or Bonucci, the Bergamo native is the type of positionally sound defender who will never make highlight reels, but is vital to his team's success.

If indeed Marotta has pipped his competitors to this signing, it will be just the latest in his ever-growing resume of impressive deals.