Milik is set for a break of four to six months from football after undergoing knee surgery in Italy on Monday, according to reports.
The 23-year-old Poland international, who plays for Italian side Napoli, damaged the anterior cruciate ligament in his right knee during a Serie A match against SPAL on Saturday.
In October last year, Milk ruptured a ligament in his left knee while on international duty with Poland.
He returned to action after about four months.
His latest injury means that Milk, who has 36 caps, will be sidelined as Poland wind up their campaign to qualify for next year’s World Cup in Russia.
Milik had been called up by manager Adam Nawałka for the national squad’s last two qualifiers -- against Armenia in Yerevan on 5 October and Montenegro in Warsaw on 8 October.
Among messages of support for Milik from teammates was one from Poland captain and Bayern Munich star Robert Lewandowski, who tweeted: "Put up a fight! Our real strength is how we rise up after defeats! I hope you will turn yours into a success."
Midfielder Grzegorz Krychowiak, who plays for English Premier League side West Bromwich Albion, wrote on Facebook: “Arek, you will come back stronger after this injury, I'm sure. Everyone's waiting for you to be back. We're there for you. Forza Milik!”
Manager Nawałka wrote: "We believe that Arek Milik will quickly be back fully recovered. He is a young, very strong and determined player. I believe he will be back with us soon. Arek, we are with you! Come back to us!”
Milik replied on his Facebook profile on Monday evening: "Thanks for all your messages and words of support. It means a lot to me. You’re helping me a lot this way. Now I’m focusing on steadily getting back and training. Keep your fingers crossed for me. I’ll come back stronger."
Poland are well on track to qualify for next year's tournament in Russia, which begins in mid-June. They are top of their qualifying Group E on 19 points, three points ahead of Montenegro and Denmark, with two games remaining. (gs/pk)
Source: Polish Radio, PAP