The £65m striker had his chances to open up his account, but failed to find a way past Foxes goalkeeper Mads Hermansen.
Postecoglou later said: "Yeah, he was good. He worked hard for the team.
"He had a couple of chances. He will be disappointed he didn't do better with and the overall performance of everyone was OK, but it doesn't mean anything if we don't turn that performance into outcomes.
"We had similar issues last year and if we're going to get to the next level as a team and bridge the gap to the top sides, it is an area of the game we need to improve."
The Australian also said: "We lost our composure and the crowd got behind them, but again finished strong. Just really disappointed we lacked a little cutting edge in the front third, made some poor decisions, lacked some composure and didn't get the reward our football deserved."