Diakite has featured just six times since the end of November, and Redknapp has revealed that the Mali international wants to leave the club.
The former Tottenham Hotspur boss told reporters: "Diakite wants to go. We won't stand in his way.
"He's had knee surgery and he's not fit at the moment, but we're happy to let him go."
The 24-year-old was a £3.5m signing from Nancy last summer.