Romelu Lukaku on Monday defended his decision to undergo treatment in his home country rather than at his club after pulling out of Belgium's World Cup warm-up matches in the United States.
The 32-year-old has barely played this season because of injury but said that success for Napoli and his national team were all he wanted.
"This season has been a lot for me from dealing with the injury and the personal loss (of his father)," Napoli striker Lukaku posted on Instagram.
"I know there has been a lot of noise about my situation in the last few days and it's important to clarify the whole situation...
"The truth is the last few weeks I wasn't feeling right physically and I had it checked out while I was in Belgium and it showed that there was an inflammation and liquid on my hip flexor muscle."
After an injury-disrupted season, Lukaku withdrew last Tuesday from Belgium's World Cup warm-up friendlies - skipping the 5–2 win over co-hosts the United States and missing the upcoming match against Mexico.
"I chose to do the rehab in Belgium... (But) I could never turn my back on Napoli, never," he added, in response to internal criticism from the Serie A club and their supporters.
"There's nothing more I would love to do than play and win (for) my team," he said. "But right now I have to make sure I am clinically 100 per cent cause I haven't been recently and it took a toll mentally."
Lukaku, Belgium's all-time record goalscorer, said it had "been a lot this year", but "all I want" is to "get there and help Napoli and the national team to their respective objectives".
Having suffered a thigh injury during pre-season, Lukaku did not return to competitive action until January this year.
He has made just seven appearances for the Serie A champions in all competitions this term as they have endured a tough title defence – Napoli currently trail league leaders Inter Milan by seven points.