Manchester United star Zlatan Ibrahimovic revealed his knee injury was worse than previously known, saying people would be shocked he returned.
The Swedish striker made his first appearance since April after coming off the bench in his side's 4-1 Premier League thrashing of Newcastle United on Saturday.
Ibrahimovic, 36, said his injury was far worse than previously known, although he preferred to keep the severity a secret.
"If people knew the real injury, they would be in shock that I was even playing. It was more than the knee but I will keep it personal – that's why I choose not to talk of it," he told UK newspapers.
"In my recovery I have not rushed anything. I have been out for six and half months. I have been following protocol and my schedule day by day.
"The only secret has been working hard. Those close to me know what I have been doing. I was working five, six hours a day."
Ibrahimovic scored 28 goals in all competitions for United last season before being released, only to sign a new one-year deal.
The veteran may be coming out of contract again, but he is unconcerned about his future.
"At the moment I am just thankful I can run and push it and play football again," Ibrahimovic said.
"I don't know what the future brings but what happens, happens. I am at the age where I can choose what I want to do.
"I don't sign five- or 10-year deals, I am just happy to be back playing and doing what I am good at.
"It's fantastic to be playing. Jose [Mourinho, United manager] said, 'Do whatever you want, I trust in you and you know what you have to do' so I was not worried.
"The contract is all paperwork and I do the physical work."
|Germany survive in Sochi but questions remain|
|Germany 2 Sweden 1: Late Kroos winner brings Low´s men back from the brink|
|Perisic dreaming of matching Croatia´s France 98 heroes|
|Veron questions Sampaoli for leaving Icardi out|
|Southgate won´t blame injured Alli for playing through pain barrier|
|Travelers Championship: Course invader drives Rory McIlroy and crowd nuts|
|Saul tells Atletico to renew Oblak deal after Griezmann´s new contract|
|Course invader sends McIlroy & crowd nuts at Travelers Championship|
|Saudi Arabia v Egypt: El Hadary eyes history in dead rubber|
|Referee declines Cheika invite after Australia´s series loss to Ireland|
|Griezmann, Mbappe can eclipse Henry, claims Trezeguet|
|Nawalka hopeful of Glik return against Colombia|
|Mexico outsmart South Korea to join Croatia as unheralded World Cup threats|
|´No drama´ for Southgate after England team sheet leak|
|Hend caught by five in Pulheim as Bjerregaard goes low|
|´Little Pea´ Hernandez hits big Mexico milestone in World Cup win|
|Modric and Rakitic the best midfield in Russia - Corluka|
|Cipriani and Farrell ease pressure on Jones as England avoid SA whitewash|
|South Korea 1 Mexico 2: Hernandez nets landmark goal as last 16 beckons|
|Ozil and Khedira axed by Germany|
|Djokovic plans to use two rackets against Cilic after reaching Queen´s final|
|World Cup of penalties? Russia surpasses Brazil after VAR introduction|
|Neymar ´fully recovered´ but Brazil coach Tite has thigh injury|
|Hansen claims France ´clutching at straws´ after another referee controversy|
|Douglas Costa, Danilo out of Brazil´s Serbia clash|
|Hamilton claims 75th pole as Mercedes dominate in France|
|´Mentally strong´ Salah will overcome World Cup disappointment, says Mane|
|Pekerman contemplating unleashing James and Quintero together|
|Schmidt hopes Australia furnace will produce Ireland diamonds|
|I´m missing practice, but it´s OK - Federer ready for Coric|
|Spain v Morocco: Alba makes case for the defence|
|Team-man Lukaku firmly in the race for individual prize|
|Belgium 5 Tunisia 2: Lukaku and Hazard shine as Red Devils run riot|
|Leaked England team gives Panama no advantage, insists Gomez|
|Mane and Senegal holding no fear for Japan|
|Murray to meet Wawrinka at Eastbourne|
|Nigeria goalkeeper Ikeme in remission after year-long cancer battle|
|Lukaku breaks Belgium record against Tunisia|
|Iran v Portugal: Team Melli bullish over qualification chances|
|Mauresmo to be France´s first female Davis Cup captain|
|Maradona angry at Argentina World Cup performances|
|Ireland cap stunning season with series win over Wallabies|
|Uruguay v Russia: Selection posers for already-qualified pair|
|Federer scraps his way to yet another Halle final|
|Lunin rejected ´3,000 offers´ to join Real Madrid|
|On your bike! Iceland physio sent home after cycling accident|
|Not just Real Madrid interested in Fekir, says Aulas|
|France frustrated by officials again as All Blacks complete sweep in style|
|Jose Enrique reveals brain tumour surgery|
|The referee was a disaster, fumes Matic|
|Lakmal to captain Sri Lanka in Chandimal´s absence|
|Alli back in England training|
|McIlroy, Watson plotting moves as Harman leads Travelers Championship|
|Tearful Neymar is a joyful boy, says Jesus|
|Ruiz: Coutinho has the same quality as Neymar|
|Kovacic announces intention to leave Real Madrid|
|Red Sox edge Mariners in 34-hit extravaganza|
|Marquez asks Mexico fans to ´let them rest´|
|Fabregas hopeful of Spain recall|
|Milinkovic-Savic plays down Juventus speculation|
|Rashford inspired by Ronaldo|
|Messi is not a leader, he is no Ronaldo, claims Petit|
|Better than Ballack? Hodgson backs Loftus-Cheek to shine against Panama|
|Svitolina and Garcia suffer upsets|
|Walker responds to Ferdinand criticism|
|Djokovic still hungry for more after reaching major milestone|
|Ellis drop goal earns Castleford dramatic win|
|Nigeria hero Musa unsure on Leicester City future|
|X marks the spot - Granit´s rocket sets World Cup first|
|Xhaka and Shaqiri follow the script as Serbia are derailed|