Former MK Dons midfielder Keith Andrews is to take up a full-time coaching role with the club this season.
Midfielder Gary Deegan has signed a new one-year deal at Southend.
The 20-year-old has yet to make a first-team appearance for the Premier League outfit but he has experience of playing in the Football League.
He turned out 14 times for Tranmere during his loan spell at Prenton Park in the 2012/13 campaign, scoring one goal.
The youngster also scored once while on loan at Gillingham last season, where he made three appearances.