The January transfer window means something different to each club.
For the bigger clubs, it represents a time to reinforce their squads for the latter stages of league title run-ins and European knockout rounds. For smaller teams, signing new players takes a back-seat to securing what they already have for another five months.
Celtic fall somewhere in the middle of the two.
Certainly, the January window denotes a time to enhance the current squad. But given the club's transfer policy of signing young and selling for a profit, it has also become a time to ensure no big players leave mid-season.
This time around could see stalwarts Joe Ledley and Georgios Samaras urged out the door at Parkhead if talks over new contracts for the pair do not bear fruit.
But, traditionally, the January window has proven a shrewd time to bring in new players for the Bhoys.
From short-term signings like Craig Bellamy in 2005, to more recent examples in tune with the new transfer policy such as Ki Sung-Yueng in 2010, January has been a good mistress to Celtic.
Neither Bellamy nor Ki make the list, but read on as we take a look at the five best January signings the club have made in the past 10 years, as adjudged by price tag and overall contribution to the team during their time in the Hoops.
Joined: January 2010
Robbie Keane arrived from Tottenham at the very last second of the January 2010 transfer window on a six-month loan.
The Hoops had already, more or less, surrendered the league title to Rangers that season. Nevertheless, even on loan, Keane was a coup.
His intelligence, movement and finishing were simply a class above anyone else in Scotland's top league, with this particularly fine solo effort against St Johnstone just one example of his elegance shining through in an otherwise lifeless period for the club.
As the league was lost and the team suffered a humiliating exit to Ross County in the Scottish Cup, Keane left after his six-month loan with no silverware to show.
Regardless, he was the last Celtic No. 7 to perform with the class associated with the famous shirt and won the club's Player of the Year award despite arriving mid-season.
Joined: January 2012
Despite a distinctly unpromising start to his Celtic career following his Bosman transfer from Rosenborg, Mikael Lustig has since proved one of Neil Lennon's best recruits.
The Sweden international has demonstrated he can be counted on in the biggest games, with standout performances in the Champions League this season securing that reputation.
Others around him faltered in Europe this campaign, but Lustig came away from the club's lacklustre group stage as one of the few who obviously have the quality to hold their own in the top club competition in the world.
Niggling injuries still restrict his playing time—the BBC report he has been ruled out until April after undergoing a hip operation—but his overall game, going forward as well as defensively, has substantially improved since he joined two years ago.
At 27, Lustig may well move on from Glasgow in the next year or so, but while he is still there both Lennon and the Hoops fans alike can take comfort in the knowledge he will very rarely let them down.
Joined: January 2008
Barry Robson was 29 when he joined Celtic from Dundee Utd—so it's almost a certainty that he would not have been purchased under the current transfer system.
Yet, without him, it's almost certain the Hoops would not have won the league title in 2008.
It was the midfield duo of Robson and Paul Hartley—another January signing, from the previous year—which drove the side to seven successive victories in the final stages of the league campaign.
Far more than just the battler he was portrayed as, Robson had more-than-decent technical ability with his left foot.
From scoring with his first touch in a Celtic shirt to dispatching a winning penalty against Rangers to turn the tide in the 2008 title run-in, Robson won over most of the Hoops fans who questioned his signing.
When he departed for Middlesbrough in January 2010, it was viewed simultaneously as a sad loss to the team and a bad decision by then-manager Tony Mowbray.
Joined: January 2008
Fee: Loan (made permanent in July 2008)
A wonderful solo effort on his debut instantly endeared Georgios Samaras to the Celtic fans—his contribution during the title run-in of 2008 even more so.
His subsequent inconsistency and, at times, poor attitude combined to undermine that endearment for a significant number of the support.
Never a consistent goalscorer, the writing seemed to be on the wall for the Greek international in many a transfer window since his initial loan move from Manchester City.
Yet, when Neil Lennon made the change his backers had been crying out for in moving him to the left wing, Samaras' form and attitude changed completely.
His contribution—particularly in Europe—has seen his stock rise markedly among the Hoops support, while his goal scoring has become more consistent since the pressure of playing as a striker was removed.
The 28-year-old is out of contract in the summer—hence the rumours of his impending departure during this January window.
If he does leave this year, it is to his testament that no Celtic fan will remember him with indifference—such is the perpetual splitting of opinion his ability has provoked.
Joined: January 2011
Kris Commons has been a phenomenal signing for Celtic.
The ex-Scotland international had been enjoying his finest season to date at Derby County when the club paid just £300,000 to bring him north of the border.
Like Samaras, he endeared himself to the supporters virtually straight away with a goal on his debut.
Unlike Samaras, Commons has rarely let the Hoops down since—a portion of the 2011/12 season notwithstanding.
His goalscoring from midfield domestically has been remarkable—21 this season already—while he weighs in with almost as many assists.
While he has a tendency not to perform as well in the Champions League—a fair criticism, all things considered—he did send the club through to the last 16 just over a year ago with his 82nd-minute penalty.
Criticisms of his European performances aside, his importance to Celtic in domestic competitions is unparalleled.