The 23-year-old was sent off during the last meeting between the two teams at Pittodrie, with the Dons going on to win 3-1 on March 19.
Porteous was involved in the Scottish Cup semi-final defeat by Hearts last month but his sending-off in the northeast, coupled with an additional one-game suspension added on following Hibs’ failed appeal has seen him sit out the last four matches against Hearts, Dundee United, St Mirren, and Livingston.
Gray admitted it had been a risk returning the centre-back to the defence after so long out but praised his contribution.
"I thought he was fantastic; he's not played for a few weeks so it was always going to be a bit of a risk at this stage to throw him in and see how he was but he didn't show any signs of rustiness,” the caretaker manager commented.
"He's trained exceptionally well, he works really hard, and I think he's a fantastic player.
"He's had his challenges at times, and I think he knows that, but when his head is on it and he's in a good place like he is at the moment, he's a top centre-half at this level."
Gray also had sympathy for midfielder Joe Newell, who saw Joe Lewis make a stunning save from a close-range shot in the 1-1 draw on Saturday.
"I don't know what Joe needs to do to score – at least he's getting into those positions,” the 34-year-old said.
“It's a fantastic save from Joe Lewis and he made a couple in the game. Credit to Aberdeen, I thought they defended exceptionally well and threw their bodies on the line numerous times.
"I think there were seven or eight big blocks in the game so credit to them for defending for their lives at this stage of the season.
"I don't know how many chances we need to win a game of football, I think that's the frustrating side to it, but I was delighted with the team’s response to going a goal down."