Petrén injured his finger in the loss and was taken straight to hospital.
The finger was x-rayed and now the 25-year-old midfielder is forced to walk with a finger splint.
- I know it's broken, but I do not know if I should have surgery.
A broken finger is usually between 4-6 weeks, but we will see, says Petrén who has played 16 international matches.
The national team captain Tomas Axnér has not yet decided whether a replacement will be called in.
VästeråsIrsta's 21-year-old midfielder Frida Rosell is already an extra player.
- We have four talented, developable players.
It is clear that there are players in place who can replace that role, but then if there is another player who is called in, I will make a decision today, says Axnér.
Sweden thus meets Poland twice.
First in Lund on October 1 and then in Ystad two days later.
These are the first international matches since the World Cup in December last year and the start of a recharging against the European Championships in Denmark and Norway in December.