The Welshman, who turned 36 on Sunday, was at his influential best against Avram Grant's side and, although Rooney's hat-trick hogged the headlines, it was the contribution of Giggs which had the England international purring.
"He's amazing," Rooney told MUTV. "His energy, his workrate, his passing and his movement are unbelievable. It's a privilege to play with him.
"He plays more like a 26-year-old; he's up and down, he's everywhere. It's great for him to get his 100th Premier League goal. I didn't know (about the record) until after the game, but I'm delighted for him."
Rooney also took time out to praise the man on the opposite flank; Antonio Valencia, who gave Portsmouth a torrid time and continued his rapid assimilation to the United style of play.
"I think he's settling in more and he's looking much more of a threat now," said Rooney. "He's scored a few goals in recent weeks, he's big, strong, quick and if he keeps improving the way he is, he'll be a real threat for us throughout the season."