Curtis Nelson: Plymouth Argyle captain and Reuben Reid among four to leave
Plymouth Argyle captain Curtis Nelson and striker Reuben Reid have left the club after failing to agree new deals, along with full-back Kelvin Mellor and forward Tyler Harvey.
Manager Derek Adams declined to comment on the departures of the four players.
However, highly-rated defensive midfielder Carl McHugh has agreed a new deal at Home Park.
Nelson, 23, made 247 appearances for Argyle after making his debut as a 17-year-old in 2010.
He joined the club's academy, having been released by Stoke City, and became the youngest person since 1967 to captain Argyle when he led them for the first time against Cheltenham Town in April 2013.
Argyle will be able to command a compensation fee for the centre-back from his next club, as he is under the age of 24.
Reid, 27, also came through the club's academy and was in his second spell at the club, having rejoined in 2014 after spending much of the previous 18 months with Argyle on loan.
He was top-scorer in both the 2013-14 and 2014-15 seasons and became the first Argyle player in 86 years to score a hat-trick against Devon rivals Exeter City in February 2015.
Mellor joined the club in the summer of 2014 and played 93 times, while 21-year-old Harvey, also a product of Argyle's youth system, made just eight appearances last season, scoring twice in the final-day 5-0 win over Hartlepool United.
"We've got 18 permanently signed players now," boss Adams told BBC Radio Devon.
"We've still got two or three to go permanently and then we'll look at the loan signings."