Oxford manager Chris Wilder reserved special praise for former Portsmouth 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 a 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."
Pompey boss Guy Whittingham is not reaching for the panic button just yet despite his side's dismal start.
He said: "This is a whole new team we have put together and they will take time to gel. This is only the first day and there is a long season ahead.
"For 35 minutes I thought we were doing well and looked a good team but in the end I think the emotion of the day got to us.
"The crowd were desperate for us to win and the noise they generated was unbelievable at times.
"The red card changed the game. At that stage we were 2-1 behind and we felt we could get back into the match but when Johnny went, we fell away."