When a player wants a transfer, clubs are often powerless to prevent it.
Some refuse to play, some go AWOL, and some publicly pursue an exit. Either way, the club usually loses.
Taylor Swift knows how to sniff out trouble, and so do we. Here are 11 players who know how to create problems for their club.
GK - Thibaut Courtois
As many fans of Chelsea, Genk and Atletico Madrid will tell you, Thibaut Courtois causes problems. He famously refused to play for Genk to force through a move to Stamford Bridge, before doing the same to get his move to Real Madrid. Kissing the badge of his new team certainly didn't impress the Wanda Metropolitano faithful.
Zinedine Zidane is back, and so is Keylor Navas, who has taken the Belgian's place in the lineup. Courtois will certainly not be happy about that, and that spells trouble.
RB - Isaac Hayden
On the field, Isaac Hayden has been a model professional for Newcastle. However, away from the pitch, he has been very outspoken in his desire to leave the club, with Sky Sports citing family reasons.
His wish was not granted in either of the last two transfer windows, and the Magpies have taken a huge risk in keeping an unsettled player around the club for so long. As of yet, he has not caused any serious issues, but such a situation could boil over at any given moment.
CB - Andreas Christensen
Andreas Christensen went from 'first-team star' to 'bench warmer' over the summer, which was understandably hard to take for the Chelsea man. According to Metro, his agent has threatened to force a move away from the club for Christensen if he does not get more opportunities.
The player himself told Bold that he had doubts over his future at the club and, with Maurizio Sarri showing no signs of wanting to replace either David Luiz or Antonio Rudiger, those doubts will likely grow.
CB - Sergio Ramos
Few players divide opinion amongst fans like Sergio Ramos. Controversy follows the Spaniard like a shadow, and that looks set to continue. Recent weeks have seen Ramos linked with an exit from Real, and reports of a dressing room bust-up with president Florentino Perez will only keep the rumour mill turning.
According to Marca, Perez threatened to banish Ramos from the team, and the defender responded by insisting he would have no regrets if he met such a fate. All is not well at the Santiago Bernabeu.
LB - Marcelo
Once regarded as the world's finest left-back, Marcelo has endured a tumultuous campaign. Poor form saw him lose his place in the team to young Sergio Reguilon, and the problems have only mounted ever since.
The Brazilian reportedly began pushing for a move to Juventus, whilst his wife also took to social media to hint that Marcelo was unhappy. Could he be yet another casualty of Real's disastrous season?
CM - Adrien Rabiot
Adrien Rabiot is not a Paris Saint-Germain player. According to his mother, Adrien Rabiot is a Paris Saint-Germain prisoner. Veronique Rabiot's emotional interview with L'Equipe is just the latest turn in his unhappy transfer saga, and it seems only a matter of time before Rabiot is on his way out.
Initially believed to have been frozen out of the team for refusing to sign a new contract, Rabiot has since been suspended after being caught partying following PSG's Champions League exit. Not much else could go wrong for Rabiot who, for one reason or another, is in a pretty dire situation.
CM - Radja Nainggolan
Another player who is no stranger to controversy, Radja Nainggolan is not afraid to make enemies in football. The Belgian has had his differences with national team manager Roberto Martinez, and recently opened up about his clash with sporting director Monchi whilst at Roma.
Nainggolan felt disrespected by Monchi's attempts to sell him, so took matters into his own hands and forced through a move to Inter. He even admitted that he was prepared to start a war every day until he was granted his release. Probably best not to get on his bad side.
CM - Idrissa Gueye
Idrissa Gueye deserves credit for his response to PSG's interest in him in January. The Everton man has remained passionate on the pitch, but fans will certainly be worried by his desire to join the Ligue 1 side.
He admitted that a move to PSG was like a "dream" for him, revealing he was ready to make the switch after handing in a transfer request. The Parisians rarely accept defeat in the transfer market, and Gueye's positivity will likely be tested this summer.
RW - Antoine Griezmann
Poor Atletico Madrid. Los Rojiblancos spent much of the 2017/18 campaign dealing with Antoine Griezmann's reported desire to leave the club for Barcelona, and it looks as though they will have to brace themselves for round two.
The Frenchman is said to have began offering himself to Europe's top sides, even apologising to Barcelona for snubbing their interest last summer. Two years of almost constant desire to leave means Griezmann has almost become one of the world's most troublesome players.
ST - Mauro Icardi
When you think of controversial footballers, chances are you've probably pictured Mauro Icardi. Talks over a new contract at Inter seem to have spectacularly stalled, and Icardi has not been seen since being stripped of the captaincy in February.
Many fans refuse to believe Icardi's diagnosis of a knee injury, instead believing that the striker simply wants out. After years of difficulties, it might be time for Inter to cut him loose.
LW - Eden Hazard
The kind of flirting which Eden Hazard has been showing towards Real usually ends in divorce, and there is a growing fear amongst Chelsea fans that the end to his Stamford Bridge tenure is nigh.
It seems as though Hazard has spent years talking about his desire to move to the Bernabeu, refusing to sign a new deal as he decides whether he really wants to spend his future in London. If this was your partner, you'd probably have kicked them to the curb.