Danny Pugh's first-half header on his second home debut for the club helped United extend their unbeaten run in the Championship to four games, but it was at the other end of the pitch where Grayson got the most satisfaction, with the latest in a long line of cobbled-together back fours finally keeping the opposition score at nil.
Last weekend's 3-3 draw at Brighton - Leeds had led 2-0 but had to score an injury-time equaliser - prompted Grayson to make a rare public criticism of his defenders, and he was joined in midweek by outspoken owner Ken Bates who also demanded better than 15 goals conceded in eight games.
And after bringing back the previously-ostracised full-back Paul Connolly for a first appearance in a month and moving rookie Tom Lees into his more natural central position, the Whites managed to heed their warnings, leaving Grayson a happy man.
"One or two of them were on their last warnings after last week," he said of his players.
"I criticised the back four and I don't normally do that, but I felt it was time that people took responsibility for what's happened and they responded in the right manner.
"It was a good performance from us, I'm delighted that we kept a clean sheet for the first time this season.
"The players have taken on board what we have worked on this week.
"When they were called on the defenders defended and the goalkeeper made some good saves. We're trying to get the right balance between attacking and defending and we're delighted to keep the clean sheet.
"You have to be able to see stages of a game through and be determined and professional. We've probably been a bit naive, going gung-ho for the next goal, but we needed to be professional and we were."
Portsmouth have picked up just nine points from their 10 games this season, but despite improving on a torrid first-half performance after the break, they were unable to find a way past Andy Lonergan.
And despite enjoying the better of the possession in the second half, Pompey were unable to create the chances they did in the first - Greg Halford hitting the bar also forcing a stunning save out of Lonergan - and manager Steve Cotterill felt his side showed signs having played three games in eight days.
"In the second half, we were much improved," he said.
"In the first half we looked like it was our third game in eight days and they looked fresher than us for not playing in midweek.
"But the way we played in the second half makes it harder to understand why we were so lethargic in the first.
"It was the first goal we've conceded from a set-piece, and if someone loses their man there is not a lot you can do."