The Croatian striker converted from the penalty spot in the 10th minute to open the scoring against reigning champions Manchester City to mark his first goal since his opening weekend double in the 5-0 win over Norwich City.
Despite the early goal, Fulham eventually lost 2-1 to City at Craven Cottage and Petric felt he and his teammates allowed their opponents to dictate play too much.
"Of course I'm happy to be back scoring again," Petric told Fulham's official website. "It's always good for a striker to score. I had a good start to my Fulham career but then I was a bit injured. I'm happy to be back now and of course I'm happy about my goal but I wasn't really happy because we didn't win.
"We were not too pleased with our game in the second half - I think we were too deep and they had a lot of possession and we needed to be a bit braver. We defended very well but at the end it was a pity that they scored.
"Of course it's hard to play against footballers as good as that but we shouldn't have let them play as much as they did. If we'd managed to keep the ball a bit more then it would have been a different game but they were better than us on the day and probably deserved to win."