Pompey have signed versatile midfielder Tom Naylor on a three-year deal.
The 26-year-old – who is also comfortable in defence – will officially become a Blues player on July 1 when his contract expires at Burton.
Blues boss Kenny Jackett said: “It strengthens the spine of our side, while he also brings us recent Championship experience.
“Tom’s a ball-winner and I feel that he’ll complement the other talented players we already have at this club.
“He’s someone who can play in a variety of positions, although he’s primarily been brought in as a defensive midfielder.
“We do feel that the squad is being improved this summer and we’re getting to where we want to be.”
Naylor joined Burton in the summer of 2015 following a spell on loan and made a total of 134 appearances for the Brewers, scoring 13 goals.
He began his career at Mansfield and has also turned out for Derby, as well as having temporary stints with Bradford, Grimsby, Newport and Cambridge.