Yet this season he has not only had to contend with the forays of opposition strikers, but also racist attacks from rival fans.
A Frenchman born to Senegalese parents, Koulibaly was subjected to “animal noises” from kick-off when Napoli took on Inter Milan in December.
With just under ten minutes left in the match, his frustration at the referee’s failure to act finally got the better of him. Koulibaly was sent off for sarcastically applauding the match official, his tormentors continuing to jeer him from the stands.
When their punishment did arrive, however, it was swift and severe – Inter were ordered to play their next two home games in an empty stadium, the club and all its supporters held accountable for the behaviour of a vocal minority.
It is this strict liability model which some believe could rid Scottish football of anti-social behaviour and its own peculiar scourge: sectarianism.
But its introduction – or imposition – would probably be unpopular with clubs and some fans who feel increasingly under attack following the introduction of the Offensive Behaviour Act.
Over the past 20 years, Scottish football’s periodic bouts of soul-searching over sectarianism and fan behaviour have become as predictable as the national team’s failure to qualify for major tournaments.
After an ill-tempered Old Firm match in 2011 – the latest in a long line of “shame games” – the Scottish Government took the matter out of the hands of the football authorities, introducing the Offensive Behaviour at Football Act.
The legislation achieved the kind of consensus among fans, clubs and politicians that had hitherto proved elusive – nearly everyone hated it.
Sir Tom Devine, one of the country’s most respected historians, described it as the “most illiberal and counterproductive act passed by our young parliament to date”.
Despite being repealed last year, the legislation has nevertheless managed to leave a toxic legacy among some fans who feel they are being unfairly targeted by the police.
Meanwhile, none of the game’s problems have gone away, with a small number of incidents over the past few weeks generating headlines for all the wrong reasons.
Last month, Kilmarnock’s Catholic manager Steve Clarke said Rangers supporters had subjected him to abuse from the “dark ages” during a game at Ibrox, while striker Kris Boyd accused Celtic fans of calling him an “Orange bastard” and hitting him with a coin at Rugby Park.
Other incidents include a glass bottle being thrown at Celtic player Scott Sinclair during a game against Hibs at Easter Road, a Hibs fan running on the pitch to confront Rangers captain James Tavernier and allegations that Hearts players were subjected to racial abuse during a game with Auchinleck Talbot.
Amid all this, one of the country’s most senior police officers expressed concern at the level of sectarianism in the Scottish game, describing it as “almost visceral”.
Deputy Chief Constable Will Kerr, who began his career in Northern Ireland during the Troubles, said there had been a rise in sectarian abuse and offensive behaviour at football grounds during the past year, although he admitted it was hard to “quantify empirically”.
It all means that strict liability, allowing clubs to be punished with fines, stadium closures and even points deductions for the behaviour of their fans, is back on the agenda.
Professor Duncan Morrow, who led an advisory group on tackling sectarianism on behalf of the Scottish Government and published a report on the issue in 2015, is an advocate of strict liability, but only as a “last resort”.
“Self-regulation is by far the best outcome, but the glaring inconsistency between the way racism is handled and the way sectarianism is handled in Scottish football is now becoming too visible to be overlooked,” he says.
“Legislation can be a blunt instrument, but eventually you have to come up with some sort of legislative framework. Strict liability and the way it is approached in other parts of Uefa [European football’s governing body] in relation to racism, has to be on the table.”
Morrow’s original report described sectarianism as a “deep-rooted and serious problem” across the whole of Scottish society which was being perpetuated by a “culture of denial”. And in a 2017 follow-up report he accused the football authorities of “frustrating” attempts to tackle the problem.
The academic, who is based at Ulster University, says the “normalising” of sectarianism has resurfaced again in recent months, with the political climate around Brexit helping to encourage more extreme forms of hate speak.
“The tolerance for hate speech has been made worse by the political climate we’re living in,” he says. “Brexit in that sense is very much the central issue.
“The issue of sectarianism isn’t particular to football, but football needs to take a role. The strong preference is that football sets its own house in order. Strict liability is what you get to by default.”
Yet Scotland is by no means the only country facing problems over football. In fact, following the game in Scotland is undoubtedly safer than in some other countries in Europe, where serious disturbances remain common.
Fan violence has marred recent matches in Italy, Poland and the Netherlands, while Aston Villa player Jack Grealish was attacked by a fan during his club’s derby match with Birmingham City earlier this month.
Nevertheless, a 2016 survey by FIFPro, a players’ union, put Scotland second only to Congo as the league with the highest proportion of players (33 per cent) who had received a threat of violence from a fan on match day.
Paul Goodwin, of the Scottish Football Supporters Association, says many law-abiding fans now want the clubs to act.
And he says strict liability has been shown to work in tackling problems with racism and homophobia elsewhere.
“In various places, from South America to eastern Europe, sanctions have been applied and racism and homophobia no longer surface at football matches,” he says. “Is it still there in places like Russia, Greece, Turkey and Bulgaria? The answer is yes, but football is no longer used as a vehicle.”
Goodwin says his organisation plans to survey its members soon on the introduction of strict liability.
“We think it’s got to be explored in Scotland. Scotland’s international matches are being played under strict liability, our clubs’ European games are played under strict liability. How can we be happy to play a game under strict liability in Madrid but not in Motherwell? It makes no sense whatsoever.”
The charity Nil By Mouth, which was set up following the sectarian murder of Celtic fan Mark Scott in 1995, agrees.
“Scottish football has been trying to bury strict liability ever since it was first mooted back in 2013,” says director Dave Scott. “It scares clubs because they presently enjoy the invisible touch of self-regulation.
“No-one is saying that strict liability is going to be a magic bullet, but the choice for Scottish football is stark: be part of the solution or continue to be part of the problem.”
For some supporters, however, it is the police that are the problem.
There is resentment over the apparently increasing use of filming during matches.
And when officers in South Ayrshire last month tweeted about confiscating a few cans of beer and half a dozen bottles of Buckfast from a supporters’ bus, they were mocked by fans from across the country.
At an Old Firm game at Celtic Park last season, five people were injured during a crush on the way into the stadium.
Eyewitnesses described a sense of panic as thoughts inevitably turned to British football’s darkest day, the 1989 Hillsborough disaster. After the incident, there was criticism of the way Police Scotland responded.
When the two Glasgow sides meet again next weekend, Rangers supporters will be required to assemble at the velodrome near Celtic Park by 10.30am before receiving a police escort to the ground.
Following the crush, Police Scotland announced an independent review of football policing, although the final report, published earlier this month, made no mention of the incident.
Its publication soured relationships between the police and one supporters’ group yet further after the Scottish Police Federation, a staff association, accused Fans Against Criminalisation (FAC) of being “apologists for criminality” for refusing to engage with the review.
In a statement released on the day of the report’s publication, the SPF said: “We concur with [report author] Deputy Chief Constable Mark Roberts that Scottish football has a hooliganism problem as well as a sectarian problem.
“They are both manifestations of the same peculiarity – that some supporter groups believe that criminal behaviour is acceptable at football matches.”
FAC’s Jeanette Findlay says the relationship between fans and the police has “absolutely broken down”.
“There’s a huge class bias here,” she says. “I hear of songs being sung at rugby which I think are disgusting. There are foul, sexually explicit songs sung at rugby and nobody cares about that.”
On strict liability, she says: “We think it’s ludicrous to suggest that large groups of law-abiding citizens should be held responsible for the actions of a tiny number who break the law and we don’t think that applies anywhere else in society.
“We’re back in the land of ‘something needs to be done’ – we never accepted that in relation to the [Offensive Behaviour] Act, and we don’t accept it now.
“In the last few weeks there’s been a whipped-up moral panic that something terrible is happening, but look at how many incidents there have been. I don’t even think there’s been five.”
Sectarianism is not a word Findlay uses. She argues Scottish football is merely reflecting society at large.
“Wider society bleeds into football,” she says. “Is Scotland an anti-Catholic country? Yes, it is. It has very thinly veiled anti-Catholic and anti-Irish sentiments right through every class and every region and that bleeds into football.”
While strict liability has its proponents in Scotland, there remain significant question marks over its effectiveness.
Inter Milan may have been punished for its supporters’ treatment of Koulibaly, but the Italian side has faced similar penalties in the past.
Rangers played in an empty San Siro stadium as far back as 2005 after Uefa closed the ground to fans for all of Inter’s group matches in the Champions League following crowd disturbances the previous season.
In Spain, where referees have the power to halt games amid racial abuse from the stands, incidents remain depressingly common.
During recent matches between Manchester United and Liverpool, fans have been heard singing songs which reference the 1958 Munich air disaster and Hillsborough, while fans of Tottenham, a club with a large Jewish following, have been subjected to anti-Semitic chants from rival supporters.
Broadcaster Jim Spence, who covers football for BBC Scotland, is among those who accept there is a problem in the Scottish game, but he remains to be convinced about whether strict liability is the answer.
He believes the solution can only be found by the football authorities – the Scottish Professional Football League (SPFL) and the Scottish Football Association (SFA) – coming together with the Scottish Government to address the issue.
“My fear with strict liability is that it takes a sledgehammer to crack a nut,” he says. “There’s no guarantee it will affect what we are seeing, which is basically criminal behaviour.
“Strict liability is a nice little earner for Uefa because of the fines it hands out, but it hasn’t actually stopped racist abuse.
“These are really complex issues. We’ve had the sectarian stuff in Scotland for a century. What we need is a meeting of minds. The SPFL, SFA and Scottish Government should sit down and nothing should be off the table.”
The police are also clear that it will take much more than one measure to rid Scottish football of sectarianism.
“The issue of sectarianism is not one you can easily arrest or legislate your way out of,” says DCC Kerr.
“Sadly I had a lot of experience of this in Northern Ireland. It’s not on the same scale in Scotland, thank goodness, but it seems to be pervasive in certain elements of Scottish football.
“I wouldn’t disagree that there’s a lot clubs can do to address this issue through deterrent tactics, more punitive tactics.
“Of course there’s a responsibility on the clubs to do that. But just because the behaviour manifests itself in football stadia doesn’t mean it’s only the responsibility of clubs. We all have a responsibility in this.”
Asked for its position on strict liability, the SPFL said it would “continue to engage with key stakeholders to help tackle all criminality occurring at SPFL stadia”. The SFA did not respond to a request for comment.