Leon Constantine may also be allowed to move on after making only seven appearances for the Whites last season.
All three players have one year remaining on their contracts at Elland Road, and Westlake and Constantine spent time on loan with Brighton and Oldham respectively during last season.
Centre-half Matt Heath has already left to join Colchester United after a successful loan period.
Leicester City's Alan Sheehan and Crystal Palace's Dougie Freedman, meanwhile, have returned to their parent clubs after loan spells at United, though Leeds are expected to make a move to sign Sheehan permanently this summer.
The 21-year-old left-back is out of contract at the Walkers Stadium but has been offered a new deal by Leicester and could command a transfer fee as a result of his age, while the prospect of Freedman joining Leeds for a second time may depend on the striker's personal circumstances.
Freedman's family are based in London, and the 34-year-old still has responsibility for coaching Palace's reserve team.
He scored six goals in 14 matches during United's run to the play-offs, however, and proved to be a massive hit with the Leeds support.