Shakhtar Donetsk captain Darijo Srna says he will not play again until he clears his name after reportedly failing a doping test.
The 35-year-old former Croatia captain revealed he had been informed by Ukraine's anti-doping body that he reportedly failed an out-of-competition test on March 22 this year.
Srna insists he has never knowingly taken a banned substance and is cooperating fully with authorities in a bid to clear up the matter.
In a statement released via Shakhtar's official website on Friday, he said: "On September 18 2017, I was notified by the National Anti-Doping Centre of Ukraine (NADCU) that a prohibited substance was reportedly found in an out-of-competition sample I had provided on March 22 2017.
"Firstly and most importantly, I would like to make it clear that I have never knowingly or intentionally taken any prohibited substance, nor unfairly intended to gain a competitive advantage. I am investigating the possible source of the substance and am cooperating fully with NADCU in this respect.
"In order to focus on my defence and avoid any undue distractions for the team, I have made the decision to refrain myself from playing until the ongoing legal proceedings have been resolved. I will now be focused entirely on clearing my name and reputation.
"Over the course of my entire career I was always under the impression that I had to persistently prove myself over and over again.
"Today is another such example when I will once again prove that everything I have accomplished, thus far, both in my life and my professional career, has been achieved solely through hard work, integrity, discipline, and honesty above all. These are the principles which were instilled in me by my late father, and are the same principles by which I am raising my own children today.
"Due to the confidentiality of the legal proceedings, I am not able to comment any further at this stage.
"I would like to thank first of all my family, the club and our loyal fans for their continual support in this matter and look forward to being back on the pitch as soon as possible. This is not the end of my career, I can promise you that!"
Srna has enjoyed huge success since joining Shakhtar from Hajduk Split in 2003, winning nine top-flight titles in Ukraine and the 2008-09 UEFA Cup among a host of honours.
He won a record 134 caps for Croatia before announcing his international retirement following Euro 2016.
|Konta splits with coach and ends season|
|Rose: No desperation for Woods return|
|Top of the range - Spieth presents Birkdale with iconic three iron|
|Oldham appoint Wellens over Scholes, Seedorf|
|FA apologises over Sampson remarks to Aluko and Spence|
|F1 Raceweek: Hamilton on the brink, but Vettel has American pace - United States GP in numbers|
|Former Springbok Smith announces retirement|
|Montella willing to accept ´exaggerated´ Milan criticism|
|Red Bull developing early to avoid slow 2018 start, says Ricciardo|
|Napoli confirm Insigne adductor strain|
|Urawa Reds 1 Shanghai SIPG 0 (2-1 agg): Rafael Silva books Al Hilal decider|
|Not a tragedy if Italy miss World Cup, says Zola|
|Milner-Skudder undergoes surgery on injured shoulder|
|Hummels: Bayern players contributed to Ancelotti´s sacking|
|Dzeko considers Chelsea among Champions League contenders|
|Joshua desperate to show new skills to build a legacy|
|Cavani doesn´t need to be friends with Neymar|
|Te´o likely to miss England´s November internationals with ankle injury|
|Ozil and Sanchez committed to Arsenal, Mertesacker claims|
|Gatland targets Super Rugby role after 2019|
|Hazlewood confident over Ashes fitness despite missing Sheffield Shield opener|
|Don´t stress it - De Bruyne relaxed over initial Man City contract talks|
|Kerr laments Green injury after Warriors lose season opener|
|Nagelsmann´s path will lead to Bayern, says Heynckes|
|Stones satisfied with strong Manchester City showing|
|Rockets stun Warriors, Hayward suffers gruesome injury in Celtics loss|
|Irving and LeBron shaken by Hayward injury|
|Yankees level Astros series, Dodgers take 3-0 lead|
|Aldridge praises Popovich after Spurs renewal|
|Redknapp: Spurs boss Pochettino could manage Real Madrid|
|Wallabies to host three-Test series against Ireland|
|That will be hard to beat – Klopp revels in record win|
|Cowboys RB Elliott eligible to play after latest court ruling|
|Bulls´ Mirotic out indefinitely after fight with team-mate|
|Spurs showed they can compete with elite - Pochettino proud after Madrid draw|
|Ballon d´Or? We all know Messi is best, says Valverde|
|Players rally around Hayward after sickening injury on Celtics debut|
|Celtics´ Hayward suffers ankle fracture|
|He´s getting better – Zidane backs Benzema|
|Napoli star Insigne unsure if he´ll be fit to face Inter|
|Manchester City can win Champions League, says Napoli boss Sarri|
|Iguodala out of Warriors´ season opener against Rockets|
|LeBron to play in Cavs´ opener against Celtics|
|Sharapova and Kerber suffer first-round exits|
|Berizzo plotting Sevilla´s revenge after Spartak Moscow humiliation|
|Porto boss Conceicao defends Casillas omission|
|We know it´s difficult now, admits Dortmund boss Bosz|
|Krajinovic denies Rublev happy homecoming in Moscow, Ferrer through in Antwerp|
|It´s tough but it´s not over - Van Bronckhorst|
|Monaco know it will be difficult to qualify now, says Sidibe|
|I don´t know what happened - Sarri bemused by Napoli´s slow start|
|We are growing consistently, insists upbeat Zidane|
|Holders Tenerife respond with win over Ludwigsburg|
|I want to stay at Saracens – McCall not interested in Test job|
|Guardiola hails ´perfect´ City after beating ´one of the best´|
|Real Madrid can´t be happy with Tottenham draw, says Navas|
|Klopp heralds counter-pressing as Liverpool run riot against Maribor|
|Liverpool break record in Maribor thrashing|
|City style fades but newfound steel gives Guardiola reason to believe|
|Ederson kept us in it - Walker relieved after City´s second-half wobble|
|Emery backs ´intelligent´ Mbappe to respond|
|APOEL 1 Borussia Dortmund 1: Sokratis header spares Burki´s blushes|
|Feyenoord 1 Shakhtar Donetsk 2: Bernard brace piles pressure on Van Bronckhorst|
|Monaco 1 Besiktas 2: Tosun double pours more misery on Jardim´s men|
|Spartak Moscow 5 Sevilla 1: Clinical second-half show stuns woeful Spaniards|
|RB Leipzig 3 Porto 2: Hosts claim maiden Champions League victory|
|Maribor 0 Liverpool 7: Salah and Firmino doubles inspire rampant Reds|
|Manchester City 2 Napoli 1: Guardiola´s men see off Serie A leaders despite second-half scare|
|Real Madrid 1 Tottenham 1: Ronaldo on target as Lloris heroics earn point|
|´Older, better´ Dzeko feeling good on return to England|