Steven Hammell has returned to Motherwell after completing a £110,000 move from Southend.
The left-back joined Southend in June 2006 on a free transfer, but Well boss Mark McGhee has been keen to take the player back to Fir Park.
The Shrimpers had rejected an offer from Motherwell on Wednesday, however they have now decided to sell as the 25-year-old's family has struggled to settle in England.
"We offered Stevie a new contract a month ago," Southend boss Steve Tilson told the club's official website.
"But to be honest his family hasn't been happy in England since day one, and he has wanted a move back to Scotland for a while now."
Southend have moved quickly in their bid to replace Hammell, bringing in Charlie Mulgrew from Wolves.
Mulgrew has joined on loan until the end of the season and will be available for Saturday's trip to Leyton Orient.