Danny Guthrie, Yakubu and Zat Knight are among the players leaving Reading.
Midfielder Guthrie, 28, who arrived from Newcastle in 2012, finished the season on loan at Fulham while ex-Everton striker Yakubu, 32, joined in February after three years abroad.
Goalkeeper Mikkel Andersen, a former trainee who turned professional in 2007, has not been offered a contract.
But the club is in talks with Adam Federici, Alex Pearce, Jem Karacan and Stephen Kelly.
The quartet are out of contract this summer.
Slovenian left-back Jure Travner has also been released, along with young professionals Ryan Edwards, Dan Lincoln, Jonathan Henly, George McLennan and Aleks Gogic.
In a statement on their website, the club added: "As we enter our third year out of the Premier League, the club's owners recognise the need for manager) Steve Clarke to freshen his squad.
"After a period of financial instability and with Financial Fair Play regulations in place, the owners are also making a concerted effort to get back to the sensible wage principles that have long been the club's trademark."