The French midfielder has returned to full fitness in his homeland on loan at Rennes and says he wants out at West Ham as he doesn't want to relive his time there.
Diarra was given only one start at Upton Park in the opening six months of his spell, with injury problems having an affect on his time in the Premier League.
"People expect a lot of me but it's hard to forget what happened in my first six months at West Ham.
"I am concentrating on improving my physical condition and playing for Rennes. But it is true that i don't want to relive what i went through at West Ham," he said.
Diarra said he was unprepared when he first joined the Hammers but was then ignored as a result.
"I don't blame the coach (Sam Allardyce) but rather the agent commissioned by West Ham. It is incomprehensible to buy a player, give him a three-year contract, and then ignore him.
"At West Ham, i was not prepared," he added. "When i arrived after the Euros, they put me directly with the group that had eight weeks of preparation."
The 31 year old's West Ham contract expires in 2015 and such is his disillusionment with the setup at the club, the 44-time capped France international looks certain to leave having provided a satisfactory replacement for Yann M'Vila, who joined Rubin Kazan last summer.
After joining Rennes on loan on transfer deadline day in January, Diarra said: "I have a three-year contract. I'm not unhappy financially, but I came to play, not to take an early retirement."