Oxford boss Chris Wilder reserved special praise for striker Dave Kitson after his team's crushing win over Pompey.
A record League Two crowd of 18,181 at Fratton Park saw Deane Smalley and Alfie Potter score two goals apiece as the U's usurped the lead given to the hosts by Patrick Agyemang.
Wilder's side almost got a fifth goal late on shortly after Johnny Ertl was sent off when Johnny Mullins' header came back off the post.
Marquee summer signing Kitson did not get on the scoresheet but his efforts and contribution did not go unnoticed by Wilder.
"Both our front men were a real handful. I have never seen Dave Kitson put in so many challenges, and not just because he used to play for Portsmouth - he will do it all season," said Wilder.
"We know what Kitson is about. They may not put themselves about in pre-season training but on day one of the season they are bang at it.
"We knew we had to overcome a very emotional occasion and it did not help when we went a goal behind, but once we got level we were all over them.
"As for the sending-off, there is no way any of my players would cheat in a situation like that. Ertl led with his arm and Danny Rose got smashed in the face."