The Champions League has become the single biggest annual competition in the world of football and controversial moments, such as the ones that now dominate the headlines in the wake of Real Madrid's victory over Bayern Munich, this week are never far away. In 25 years since the European Cup was replaced, here's a look at nine of the most controversial moments ever seen in Champions League games... In the days before goal-line technology, the 'Ghost Goal' scored by Luis Garcia as Liverpool...
Bayern Shafted (2017)
Real Madrid booked their place in the last four of the 2016/17 edition this week, but only after Bayern Munich were left feeling more than a little hard done to as a result of two contentious decisions from experienced official Viktor Kassai.
With the finely balanced tie heading to extra-time, Bayern were reduced to 10 men in the final moments of the 90 when Arturo Vidal was shown a second yellow card for what had appeared to be a clean tackle.
Cristiano Ronaldo was then twice visibly offside when he scored in the 104th minute and 109th minute to put Real ahead on aggregate and ultimately settle the tie. Already a player short, Bayern had no response and Real scored another on the night to win 6-3 overall.
(Un)Fair Play (2012)
Shakhtar Donetsk striker Luiz Adriano was actually given a retrospective one-match ban by UEFA for grossly flouting the principles of fair play during a group game between the Ukrainian giants and first time competitors Nordsjaelland in November 2012.
Adriano, who now plays for Spartak Moscow, was also ordered to do a day of community service to amend for his sins after he scored a goal against the Danes in a moment when Shakhtar were supposed to be returning the ball after an enforced break in play.
Instead of allowing a long kick forward to make its way to the Nordsjaelland goalkeeper, Adriano chased after it, ran through on goal and slotted it home. Shakhtar had been trailing 1-0 at the time and went on to win 5-2, with the Brazilian completing a hat-trick.
Peeping Sergio (2010)
Regardless of his vast ability as a La Masia-schooled player, Sergio Busquets has always been one to take advantage of situations in any way he can, and that was exactly what the Barcelona midfielder did during a semi-final clash with Inter Milan in 2010.
After being swatted away by an already booked Thiago Motta in the crucial second leg, Busquets fell to the floor clutching his face and combined serious play-acting with glances over to the referee to make sure the incident and his reaction had been seen.
"He always does it, I have seen it on TV and he is holding his face and then looking at the referee - it is terrible behaviour," Motta later said after receiving his marching orders, although it was Inter who had the last laugh after going on to lift the trophy in the final.
Nani Sees Red (2013)
Legendary Manchester United manager Sir Alex Ferguson was so incensed with the decision of Turkish referee Cuneyt Cakir to harshly show a red card to Nani during a 2013 Last 16 clash with Real Madrid that he refused to attend the post-match conference.
Nani had caught Alvaro Arbeloa with a high boot, although his eyes appeared to be on the ball and it didn't seem as though he had even seen the Real defender coming. There was no sympathy from the official, though, and the winger's dismissal left United to play nearly all of the second half with 10 men.
Ferguson's side were leading 2-1 on aggregate at the time and looked on course to progress to the next round, but Real made the extra player count and quick-fire goals from Luka Modric and Cristiano Ronaldo turned the tie irreversibly in the Spaniards' favour.
It's Too Loud in Here! (2011)
Robin van Persie was sent off in the harshest of circumstances when he saw red in a Last 16 encounter with Barcelona during his Arsenal days in 2011. The Dutchman was adjudged to have kicked the ball away when he took a shot at goal after being flagged as offside.
In reality, the time lapse between the whistle being blown and Van Persie striking the ball was minimal, while the aggrieved player himself claimed after the game that he hadn't even heard the referee halt play because of the deafening crowd noise inside Camp Nou.
"In my opinion it was a total joke, the sending‑off. How can I hear his whistle with 95,000 people jumping up. How can I hear that, for God's sake? Please explain me that," he complained afterwards.
Frisk Quits (2005)
Having emerged on the Champions League scene as Porto's triumphant manager in 2004, Jose Mourinho was the talk of Europe for a much more unsavoury reason 12 months later after his shocking treatment of highly respected referee Anders Frisk.
The Swedish official had sent off Didier Drogba during a Last 16 first leg clash between Chelsea and Barcelona, with Mourinho going on to lambast Frisk and falsely accuse him of illegally inviting Barça coach Frank Rijkaard into the referee's room.
Frisk then sensationally announced his immediate retirement just a few weeks later, citing threats made against him and his family by angry Chelsea fans. Mourinho, meanwhile, was handed a touchline ban for both legs of the next round.
It's a F***ing Disgrace (2009)
Chelsea were left feeling aggrieved by another Scandinavian referee in Europe several years later after Norwegian official Tom Henning Ovrebo turned down multiple penalty appeals in the second leg of the 2008/09 semi-final meeting with Barcelona.
Chelsea had opened up a slender 1-0 advantage early on the night at Stamford Bridge but were fully aware that it wouldn't be enough should the Catalan visitors find an away goal. As many as four penalty appeals, three of them clear, were waved away by the referee, and in heartbreaking fashion Barça did get their goal when Andres Iniesta bagged a later stunner.
Didier Drogba couldn't contain his anger at the final whistle, confronting Ovrebo, before yelling 'It's a f***ing disgrace!' into a nearby television camera as colleagues and stewards tried to lead him away down the tunnel.
Marseille's Expulsion (1993)
Marseille were the inaugural winners of the Champions League back in 1993 and remain the only French club to have been crowned continental champions in the entire history of the European Cup. But their sole triumph is still tainted by a match fixing and bribery scandal.
Ahead of a domestic game against Valenciennes just a few days before the Champions League final, controversial president Bernard Tapie ordered player Jean-Jacques Eydelie to contact two individuals he knew on the Valenciennes team and have them go easy so as not to inflict any injuries on the Marseille squad.
When the scandal was exposed, Marseille were stripped of their domestic title and barred from the Champions League, European Super Cup and Intercontinental Cup the following season. They surprisingly weren't actually stripped of their Champions League trophy, but the triumph has always had a black mark against it.
Ghost Goal (2005)
In the days before goal-line technology, the 'Ghost Goal' scored by Luis Garcia as Liverpool made it to the 2005 Champions League final at the expense of Chelsea was one of the very strongest arguments for it to be implemented.
In the ultimate tactical battle, the semi-final between the two English sides was always going to be decided by the finest of margins. Few could have imagined quite how fine, though, when Garcia's scuffed second leg finish was dramatically hooked away under the crossbar.
Numerous slow-motion replays and television graphics later showed that the ball probably never did cross the line, but it was ruled a goal at the time and was therefore enough for Liverpool to progress to the final in Istanbul where they eventually mounted one of the most iconic comebacks in modern football history.