Petterd kicked four goals and had four scoring assists, but an attempted goal-square mark was spoiled by Magpie Steele Sidebottom with just a second remaining in the match, resulting in a one-point win to the Pies.
Grimes said Petterd's efforts were outstanding and were again highlighted during the team's post-game review on Monday.
"He played a great game - probably the best game I've seen him play. Every time we had the ball out of half-back he was presenting up, he was free and he was splitting his man, so we were able to hit him up on the lead," Grimes told afl.com.au from Casey Fields on Tuesday.
"Obviously there was the mark at the end, but you can't blame that on him, because he was fantastic and probably kept us in the game. He was disappointed he didn't take that mark, but we all got around him and everyone explained to him that it wasn't his fault.
"He's over it now and he'll move onto next week. He was pretty happy with the way he played, which he should be, because he had a really good game."
Grimes said Petterd's form this season had been impressive, with the defender-turned-forward also kicking two bags of four goals in NAB Challenge matches.
"It's really good that he's come along this pre-season, because I think he's feeling a bit more at home in the forward line than in his first few years when he was moved around a bit," Grimes said.
Although Grimes said the Dees were gutted by the loss, he said the review showed they were heading in the right direction. The talented young Demon, who also played a fine game against the Pies, is eager to take on the winless Adelaide on Sunday at the MCG.
"We were happy with the effort we put in and we didn't concentrate on people outside [the club] saying we have no chance - we don't pay attention to that, because we knew all along we had a good shot at it," he said.
"We came out and played exactly how we wanted and it [almost] paid off, so it was shattering not to come away with the four points. We just wanted to take the game on because we felt against Hawthorn [in round one] we didn't take too many risks.
"[The coaches] were happy with the way we went about it, but now the big focus is Adelaide this week, so can we back it up? We don't want to be a team that plays one good game one week and then goes back into their old ways the next week."
