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Players who could prove the difference between success and failure, and players who will instantly be forgotten come the season end.

Which players have been the best signings in January?

Stuart Armstrong joined Celtic from Dundee United in the 2015 January transfer window. Picture: Getty

Jason Naismith - St Mirren to Ross County - 2017

In the space of 12 months Naismith has progressed to become one of the best right-backs in the top-flight. Experience playing at centre-back has helped develop savvy defensive qualities, combining those with powerful runs down the flank. The 23-year-old is a key attacking outlet for the Staggies and, at the time of writing, one of only four players to have delivered 100 or more crosses in the league this term.

Anthony Stokes - Celtic to Hibernian - 2016

The Irishman’s second spell at Easter Road was an interesting one. Six goals in 13 Championship games was good but better was expected. He didn’t strike up a great relationship with Jason Cummings. Come 21 May, however, it was a signing which was an overarching success. There was a double against Inverness CT to send Hibs into the semi-finals of the Scottish Cup. Then there was a double in the final as they put Rangers to the sword to end the 114-year cup hex.

Patrick Roberts - Manchester City to Celtic - 2016

Celtic took the somewhat unique approach of loaning the City talent on an 18-month loan deal. Despite missing an open goal in a Scottish Cup semi-final defeat to Rangers, Roberts enthralled Celtic fans with his skill and inventiveness. A classy dribbler, he was arguably the most talented player in the league to such an extent that there was a clamour from Celtic fans for the club to bring him back on a second loan.

Celtic in for Kieren Westwood as Motherwell reject Trevor Carson bid

Gary Dicker - Carlisle United to Kilmarnock - 2016

The Irishman has been a key individual for Kille, whether in the heart of the defence or midfield. His physical qualities have allowed him to stand up to those particular challenges which Scottish football throws up, and he can play a bit to. His presence was missed at the start of this campaign, not starting a game until December. In the eight games he has started Killie have lost only once.

John Souttar - Dundee United to Heart of Midlothian - 2016

It was clear that the 21-year-old required a change of scenery, his development having stagnated at Tannadice despite his young age. He has had his ups and downs at Tynecastle but has improved as both a footballer and more importantly as a defender to the point it is a certainty the club will make a substantial profit from his sale, sooner or later.

Stuart Armstrong - Dundee United to Celtic - 2015

Armstrong’s Celtic arc has been an interesting one. On arriving at Celtic Park, alongside Gary Mackay-Steven, he hit the ground running before suffering, as many did, during the club’s stasis under Ronny Deila. It was expected he would be leaving Parkhead but under Brendan Rodgers he became an essential member of the squad.

Danny Swanson - Coventry City to St Johnstone - 2015

Swanson is a conundrum. He has progressed from turning out at Berwick Rangers to playing for two of the country’s biggest clubs. Then again, it could be argued he hasn’t fulfilled his full potential. When he has been at his peak, however, is when he’s pulled on the blue of St Johnstone. His first spell wasn’t as successful as his second but provided the Saints with creativity.

Stefan Johansen - Strømsgodset to Celtic - 2014

A £2 million investment, Johansen was a shrewd piece of business. A classy midfield operator who had the running of many a midfield. An intelligent midfield player, he adapted excellently to Scottish football and played with an aggression which helped. He earned three league titles plus a PFA Scotland Players’ Player of the Year.

Adam Rooney - Oldham Athletic to Aberdeen - 2014

While the striker has question marks around his all-round play there is no denying his goalscoring ability. Since making the move he’s netted 84 goals in 179 appearances, helping Aberdeen to win the 2014 League Cup. He is a handy knack of being in the right place at the right time in the box, owing much to his reading of the game and anticipation.

Shay Logan - Brentford to Aberdeen - 2014

The full-back has been one of the most consistent performers in the Scottish Premiership in the last four years. He did enough in the six-month loan deal to be signed permanently by the Dons. He’s a capable right-back, both going forward and defensively.

Leigh Griffiths - Wolverhampton Wanderers to Celtic - 2014

One million pounds has rarely been better spent by a football club. Three short of 100 goals for the club, Griffiths has been prolific, season after season. There has been doubts about his all-round forward play but those doubts have lessened with each passing game. He is now more than a simple goal scorer.

Vangelis Ikonomou - Atromitos Athen to Ross County - 2013

It became a running joke in Scotland regarding the January transfer window and Ross County. They would bring in a raft of signings to propel them up the league. The Greek left-back was one of most admired players brought in by the club with the Staggies finishing in the top six in his first (half) season. He returned a second time but wasn’t as consistent.

Esmael Goncalves - Rio Ave to St Mirren - 2013

Isma gave a snapshot of both his qualities and deficiencies in a loan spell in Paisley. He saved his big moments for cup outings, scoring three goals in two Scottish Cup games before playing a pivotal role in St Mirren’s League Cup success. He opened the scoring in the semi-final against Celtic before drawing the Buddies level with Hearts in the final.

Mikael Lustig - Rosenborg to Celtic - 2012

It is not often clubs are able to recruit a free transfer midway through the season. Even more so when they are the quality of Lustig. The Swedish international has been a dependable right-back... when he’s played. He’s suffered nine separate injuries but has still amassed more than 200 appearances and become ingrained with the club.

Henrik Ojamaa - RoPS to Motherwell - 2012

The journeyman’s most successful spell was arguably his first at Fir Park. Arriving on a free contract the Estonian scored nine times with a further eight assists in 21 games. It helped Well to a third place finish and convinced Legia Warsaw to part with a six-figure fee for his signing. His second and third spells in Scotland weren’t as productive.

Dieter Van Tornhout - Nea Salamis to Kilmarnock - 2012

The Belgian forward was, at best, limited. However, he scored the decisive goal in the League Cup final win over Celtic. For that he’ll forever be a legend at Rugby Park and one of the great January signings. It was one of only two goals for the club. The other came in a 4-2 defeat to St Mirren.

Kris Commons - Derby County to Celtic - 2011

The former Scotland international has opened up about his exit from Derby on a number of occasions. At training one day he was told that he was being sold to Celtic with little input from the player. And what a move it turned out to be - and for a snip at £300,000. He offered creativity and goals in a variety of attacking positions. His peak came in 2013-2014 where he hit 31 goals in all competitions.

Kris Doolan - Auchinleck Talbot to Partick Thistle - 2009

Okay, this is somewhat of a cheat as the Jags were not in the top-flight. But the transfer, and story, of Doolan had to be included. From junior football to helping Thistle get promoted. Not only that but has he as proven that he belongs in the Scottish Premiership, netting more than 50 top-flight goals and more than 100 in all for Thistle.

David Weir - Everton to Rangers - 2007

Few could have imagined the affect the veteran centre-back would have at Ibrox when he arrived as a 36-year-old. More than 200 appearances, three league titles, a pair of Scottish Cups and three League Cups. Not to forget a run to the UEFA Cup final. He provided experience and leadership in abundance and looked, at times, like he could have played into his 50s.

Barry Ferguson - Blackburn Rovers to Rangers - 2005

The Ibrox side parted with a substantial fee to bring Ferguson back. But there was no question Rangers were bringing back a quality player who had proven himself in Scotland before and had matured. Regarded by many opponents as one of the best players they faced in Scotland, Ferguson brought control to the middle of the park with his shrewd passing and intelligence.

20 of the best January window signings in the Scottish top flight