BEN Thompson is set to join Portsmouth to link up with former Lions boss Kenny Jackett.
Thompson, 22, will sign for Pompey on loan for the 2018-19 season, but Millwall will have the option to recall him.
Midfielder Thompson made his first appearance of the season in Millwall's 3-1 penalty-shootout EFL Cup win over Gillingham on Tuesday night.
Thompson was a regular in Millwall's side in the 2015-16 and 2016-17 seasons, but played just eight times in the last campaign.
Jackett's Portsmouth are fifth in League One after winning their first two games.
Image: Millwall FC