Midfielder Luisma Villa has terminated his contract at Barnet and returned to Spain for personal reasons.
The 25-year-old joined the Bees in 2013 and went on to score 17 goals in 62 appearances for the club, who won the Conference title last season.
"We promised him that if we were champions then he could go back to Spain on a free transfer," head coach Martin Allen told the club website.
"He is missing his family and his partner. It is a big loss."
Meanwhile centre-back David Stephens has left The Hive after failing to agree terms on a new deal.
The 23-year-old featured 136 times for the north London side after joining in 2012.