Chelsea forward Mykhailo Mudryk has been provisionally suspended by the Football Association after failing a drugs test.
Mudryk, who faces a potential ban of up to four years under FA rules, said in a statement this is "a complete shock" and he has "not done anything wrong".
Chelsea have launched their own investigation and said the 23-year-old insists he "has never knowingly used any banned substances".
Mudryk, who passed a routine drugs test in August, has not been in the Chelsea squad for the last four games, with head coach Enzo Maresca putting his absence down to illness.
The Ukraine winger, signed from Shakhtar Donetsk for Β£88.5m in January 2023, last played for Chelsea in a 2-0 win at German side Heidenhem in the Conference League on November 28.
Mudryk, with three goals in 15 games this season, most recently appeared on the bench for Chelsea as an unused substitute on December 1 in a 3-0 win over Aston Villa at Stamford Bridge.
FA rules dictate a player is informed of a positive test and provisionally suspended before a decision is taken on a formal charge. Mudryk has the opportunity during this period to provide an explanation for the result.
Chelsea's statement read: "Chelsea Football Club can confirm the Football Association recently contacted our player Mykhailo Mudryk concerning an adverse finding in a routine urine test.
"Both the club and Mykhailo fully support The FA's testing programme and all our players, including Mykhailo, are regularly tested.
"Mykhailo has confirmed categorically that he has never knowingly used any banned substances. Both Mykhailo and the club will now work with the relevant authorities to establish what has caused the adverse finding.
"The club will not be commenting any further."
Mudryk, in his own statement, added: "This has come as a complete shock as I have never knowingly used any banned substances or broken any rules, and am working closely with my team to investigate how this could have happened.
"I know that I have not done anything wrong and remain hopeful that I will be back on the pitch soon. I cannot say any more now due to the confidentiality of the process, but I will as soon as I can."
Anti-doping breaches are 'strict liability offences'
Sky Sports News chief reporter Kaveh Solhekol:
"I think what's important in this case is the 'A' sample has tested positive. We are still waiting the result of the 'B' sample, so I think that is very important for Mykhailo Mudryk.
"He has missed the last five games for Chelsea. Enzo Maresca, when he has been asked about Mykhailo Mudryk's absence, has said that the player is ill.
"In the meantime, Chelsea have launched their own investigation - and it should be noted that the player did pass a routine anti-doping test in August.
"It's important to stress as well that anti-doping breaches are strict liability offences. That means you as a player are responsible for what is in your body. It does not matter how it got there - it is a strict liability offence.
"Mykhailo Mudryk himself has been on social media. He said that he is in a state of complete shock. He said he never knowingly used a banned substance, and he says he's done nothing wrong and hopes to be back on the pitch on soon."
Peyadlst
0
Some people are making hateful statements because of the hatred they have for Chelsea FC
Abuela
1
He looks like jesey pink man of breaking bad....
cibbiknpu
0
some people jealous Chelsea they well so[ko]
cibbiknpu
2
super Star mudryk
TheOddOne
1
i feel Clubs should just regular test their players and check whether they consumed any wrong stuff
Besbeiruy
3
Chelsea fan's we gonna miss you allot
Lidbeklruy
1
this does not involve Arsenal as some are making fun of it , this player snubbed Arsenal for Chelsea and we are totally not involved in this saga
hubabdlt
1
he will bounce back
neucdkrtuy
0
him be back soon
27901180(deleted)
0
Disgusting drug cheats deserve no sympathyβ¦
Jaecdrstuy
0
but why to my team π π’
hinbelnrtz
0
All the best but only you know the truth
repdmort
1
i hope he will back soon
Gjsjfjfjgmgkdjfngnfk
0
he will take everything serious now
ritcestuyz
1
Enzo Maresca must be suspended for lying about the absence of Mudryk
Cukcdlpsuz
2
hes starting again but bad behavior can you stop please
ChelseaFanΒ₯21
4
ππππππππ°ππππ ARSENAL ARE BEHIND THIS !
huaaenpyz
1
Good prayer
Talento1997
1
man u wey nosabi ball
pelebe
0
I wonder why you guys are defending the number one flop of the year, in my opinion Chelsea is cause of the player's problem, they are pressuring him to perform and he feels he could only do that by taking an enhancement to satisfy his club, ππππππ it's just unfortunate he was caught. There's no need for any retest as the B sample will surely be positive πππ
I think you need to read well, he's still under investigation, he has not been find guilty, so stop running your mouth!
Purna-Shahi
2
π€π€
Suwbeoprt
1
coll π€
faaaelru
2
I wonder why you guys are defending the number one flop of the year, in my opinion Chelsea is cause of the player's problem, they are pressuring him to perform and he feels he could only do that by taking an enhancement to satisfy his club, ππππππ it's just unfortunate he was caught. There's no need for any retest as the B sample will surely be positive πππ
faaaelru
0
SOMEONE MIGHT HAVE PUT SOME SUBSTANCE INTO HIS DRINK ,... OUT OF JEALOUS !... AM SUSPECTING AN ARSENAL FAN OR PLAYER ..
THAT'S MY ROUMOUR.... TO EVERY ROUMOUR , THERE IS AN IOTER OF TRUTH
I REST MY CASE !
what's there to jealous Mudryk for? For being a flop at Chelsea? Because that's the only remarkable thing I can remember about him after joining the club
yuwbilmtz
2
mudryk can't take drugs
rihaknpru
2
they mean Ant-doping or some, where is his performance !!
Jenenpstuz
4
he will be back soon
faaaelru
0
it's shock me too mudryk , I hope sample B will be negative
Sample B is positive already πππππ
yuwbilmtz
1
Really mudryk can't take drugs
fupceiluyz
6
Arsenal hired the Russians to "fix" this guy.
hanadmoz
6
it's shock me too mudryk , I hope sample B will be negative
danwoshy256
0
that some one is Nkuku
gatwech222
4
I hope he will back soon π
ChigozirimwisdomOnu
2
Omo normally the guy is too cool for all this shits
Sokabdoru
6
SOMEONE MIGHT HAVE PUT SOME SUBSTANCE INTO HIS DRINK ,... OUT OF JEALOUS !... AM SUSPECTING AN ARSENAL FAN OR PLAYER ..
THAT'S MY ROUMOUR.... TO EVERY ROUMOUR , THERE IS AN IOTER OF TRUTH
I REST MY CASE !
oludotunkellington
2
let the poor breath
Biwanpsy
2
they started again when they saw Chelsea moving up, but don't its gone cause
Juyemnrsz
1
No10 for Sancho π₯
Binbdinruz
1
Is because Ukrainian are trouble makers this is exactly avedence Putin is fighting trouble makers all the best Mr Putin
Sacciknsy
0
it's shock me too Mudryk. I hope the B sample test negative.
Ribbeklot
0
So Maresca lies routinelyπ€.....even the title race answers could be liesππ€
whu siad that
Ayomi55
1
no room fr racis
Ayomi55
1
no room fr racism
akiamo
2
So Maresca lies routinelyπ€.....even the title race answers could be liesππ€
Ribbeklot
2
Chelsea is COME BACK π π β€ 2GOOLI
wangai254
0
not coolββ