Andre Gray is a target for Hull but the Tigers must sell before they can buy, according to reports from the Hull Daily Mail.
The striker has been linked with a move to Humberside but no bid has come in from the recently relegated Premier League club.
That is reportedly because the Tigers are keen to offload Nikica Jelavic, Dame N'Doye and Abel Hernandez but are yet to have any takers.
Owner Matthew Benham, though, will not be taking any offers for the 18-goal striker lightly with his £4million valuation appearing to be well short of what the Bees would want.
Brentford have not come out well from their transfer dealings with Hull in the past given the Michael Turner saga.
The Bees expected a healthy sell-on when the defender moved on to Sunderland in 2009 but received less due to Paul McShane moving the other way.
The Bees also signed Nick Proschwitz from the Tigers last season but the German failed to perform at Griffin Park and was released last summer.