Making only his second start for Pompey, Glen Little was soon marauding down the right wing and his accurate cross saw Traore set up Davis for a low snap-shot on the edge of box, which Villa keeper Brad Friedel gathered well.
The tempo did not let up after the break, with John Carew - on for Heskey - testing Speroni with a snap-shot on the turn from the corner of the six-yard box.