The 24-year-old starred for Cork City last season, netting 26 goals in all competitions.
And his fine exploits across the campaign have been recognised with a place in the division's team of the season.
Sadlier, who hails from Sussex, was linked with a Blues move last week and is now out of contract following the conclusion of the SSE Airtricity League season.
Blues boss Kenny Jackett admitted the free agent is a player the club are monitoring but a deal is not imminent.
Pompey signed Ronan Curtis from League of Ireland outfit Derry City in the summer and he has been a huge hit so far this term.
Wideman Curtis has netted six times already this season for the Blues and should Sadlier join, the hope would be for him to have a similar impact.