To fans of certain clubs, a particular number can be regarded as cursed due to the disappointing performances of players who have worn it down the years.
Arguably Chelsea's most 'cursed' number in recent years is the hallowed No.9 shirt, with numerous players struggling under the weight of pressure associated with wearing a number that will forever be associated with great goalscorers.
Gonzalo Higuain is the latest player to take the famous digit and will be hoping that he does not buckle under the pressure during his loan spell in west London.
But how did the Argentine striker's predecessors get on?
2000-04: Jimmy Floyd Hasselbaink
Joined from: Atletico Madrid
Chelsea appearances: 177
Chelsea goals: 88
Chelsea obliterated their transfer record to land Jimmy Floyd Hasselbaink for £15m in 2000 after he had suffered relegation with Atletico Madrid the season before despite scoring 24 La Liga goals.
It proved to be money well spent as Hasselbaink forged a fruitful partnership with Gianfranco Zola and then more famously Eidur Gudjohnsen during his four years at Stamford Bridge.
The powerful Dutchman won the Premier League Golden Boot in his debut season and averaged a goal every two games during his time with the club.
2004-05: Mateja Kezman
Joined from: PSV
Chelsea appearances: 41
Chelsea goals: 7
Regarded as one of the most feared strikers in Europe following a prolific spell with PSV in the Netherlands, Mateja Kezman moved to Chelsea in a bid to prove he could cut it in a tougher league.
A £5m fee for a striker who had plundered 105 league goals in his previous 122 games appeared to be a snip for the Blues, but Kezman struggled badly to transfer his Eredivisie form to the Premier League.
Following one unfulfilled year at Chelsea, Kezman's career unravelled rapidly as he embarked on a nomadic tour around Europe and the Far East.
2005-06: Hernan Crespo
Joined from: Inter
Fee: £16.8m
Chelsea appearances: 73
Chelsea goals: 25
At one time the most expensive footballer in the world, Hernan Crespo had enjoyed a seven-year spell in Italian football with Parma, Lazio and Inter before making the move to England.
Injury problems hindered Crespo's debut season at Stamford Bridge and his failure to settle off the pitch in London failed to help matters culminating in a loan move to AC Milan in 2004.
Crespo scored twice in the incredible 2005 Champions League final that Milan contrived to throw away to Liverpool but then returned to Stamford Bridge for a season, helping the club win their second Premier League title.
2006-07: Khalid Boulahrouz
Joined from: Hamburg
Chelsea appearances: 20
Chelsea goals: 0
Sometimes squad numbers just don't make sense. Following Crespo's departure to Inter, someone at Chelsea opted to give Khalid Boulahrouz, a versatile but limited defender, the hallowed No.9 shirt.
The Dutchman struggled to do it justice. He was largely utilised as a closer by Mourinho, coming on to help defend a lead, but his career at Chelsea was practically ended by a horror show of a performance at White Hart Lane.
2007-08: Steve Sidwell
Joined from: Reading
Chelsea appearances: 25
Chelsea goals: 1
As above. Quite why Chelsea felt it appropriate to give the striker's number to a combative midfielder is anyone's guess, but there you go.
Steve Sidwell earned a move to Chelsea off the back of a wonderful season in the Premier League with Reading, who defied the odds to finish comfortably away from danger in their debut campaign in the top-flight.
It was a low-risk move for Chelsea as he arrived on a free transfer but just like Boulahrouz, he stuck around for only a season and left in search of greater first-team opportunities at Aston Villa.
2008-09: Franco Di Santo
Joined from: Audax Italiano
Chelsea appearances: 16
Chelsea goals: 0
Chelsea secured the services of the highly-rated Franco Di Santo after he had made a promising start to his career with Audax Italiano in Chile and he was quickly integrated into the first-team.
Di Santo was handed 16 appearances during the 2008-09 season but many of those were cameos off the bench and he failed to get off the mark or show sufficient promise to command more minutes.
Carlo Ancelotti loaned Di Santo out to Blackburn Rovers and although he managed just a solitary goal there he earned a permanent move to Wigan with whom he won the FA Cup in 2013.
2011-14: Fernando Torres
Joined from: Liverpool
Chelsea appearances: 172
Chelsea goals: 45
Didier Drogba was unquestionably Chelsea's talisman in attack, but in 2011 the club started to plan for life without the brilliant Ivorian by splashing out an English record £50m on Fernando Torres on the winter deadline day.
Torres had developed into the best striker in the Premier League and European football overall during his time at Liverpool but by the time he arrived at Chelsea, he was unmistakably past his peak.
He enjoyed some memorable moments for the Blues, most notably scoring against Barcelona in the Champions League semi-finals, but overall his time at Chelsea was unsuccessful.
2015-16: Radamel Falcao
Joined from: Monaco
Chelsea appearances: 12
Chelsea goals: 1
Radamel Falcao had failed miserably to make an impact in a loan spell with Manchester United but it seemed as though Mourinho made it his pet project to transform his fortunes by bringing him to Chelsea.
During their time together at Atletico Madrid, Falcao had been the star and Diego Costa the support striker, but their roles were reversed at Chelsea with the Colombian starting on the bench.
He scored just once in Chelsea colours, a consolation against Crystal Palace and spent most of his time at the club injured leading to him returning to Monaco. A move that worked out pretty well.
2017-18-: Alvaro Morata
Joined from: Real Madrid
Chelsea appearances: 72
Chelsea goals: 24
After what looked to be a really strong start to life in London, scoring eight goals and notching four assists in his first 11 Premier League games, Morata seemed to be in contention along with the likes of Romelu Lukaku, Mohamed Salah and Harry Kane for the race for the Golden Boot.
Despite a fantastic start to his career at Stamford Bridge, a combination of personal factors and injuries saw his initial form fall off.
After one season, the Spaniard opted to change to the No.29 after in celebration of the birth of his twins. Cynics might say that finding an excuse to escape the cursed shirt is a stroke of genius…
VanishPrasad
366
Even though he did more than most players, People still regard him as the worst No.9
VanishPrasad
281
Only this guy did well as a No.9
Hiyabdrtu
260
It's nothing to do with number 9 or whatsoever number the player (s) wearing. it depend how good are you on the pitch. so don't blame the number you wearing it.
mighty96red
165
torres has made good contributions for chelsea.He also gave good contributions to win Champions League and Europa League. So I do not think he's a worst player at chelsea. He is a great player.
prakashcr7
104
No. 9 is the curse for Chelsea. And they signed and gave the No. 9 to the player named Gonzalo Huguain who is curse in himself. 🤣🤣 Huge jersey for Higuin. 😅🤣
ChelseaFanBoy
82
No matter what I think is just a superstitious though some of the players can't play well doesn't mean that it is true..... I believe that Higuain will play well with that No.9 shirt !!! Good Luck Gonzalo Higuain !!!!