The 30-year-old wing-back, who played 22 minutes in Croatia's Euro 2012 group stage exit, said making way for uncapped Dinamo Zagreb playmaker Sammir was the "final straw" after Stimac also left him out of Croatia's opening two World Cup qualifiers.
"It was a tough decision to make but being ignored to fit in Sammir at my expense is more than I can take because I was also cold-shouldered for the opening two games with Macedonia and Belgium," Pranjic told Croatian media on Friday.
"I felt strange because Stimac told me ahead of those two games I was going to play a part in both and after I was left out, I said to myself I would walk out if Sammir was called up.
"I have nothing personal against the lad, I know he is a good player but I can't accept this way of doing things."
Sporting's Pranjic has failed to score in 45 international appearances and was last a regular starter on the left flank during Croatia's futile World Cup 2010 qualifying campaign.
Sammir, 25, joined Dinamo in 2007 after nondescript spells with several Brazilian clubs as a youngster and became one of the team's key players in helping them win a record seven successive Croatian league titles.
"This is a opportunity for him to change his lifestyle and make an impact because we know he can be a better player than he is at the moment," said the 45-year old coach.
"We also know he's had problems with his lifestyle but whether he turns a new leaf and lives up to expectations is now entirely up to him and he will have to work hard because the competition within the national team is fierce to say the least."
