The Cottagers got the jump on their London rivals by taking a three-goal lead after a brace from Dimitar Berbatov and own-goal from Clint Hill but the R’s fought back through Adel Taarabt and Loic Remy.
"It was a great game for the spectators," the Dutchman told Sky Sports.
"Overall it was a bit disappointing at 3-0 up and then you make it difficult for yourself.
"The Sidwell sending off I thought was a bit harsh, that was difficult for us. It was a bit unfortunate.”
He added of his tenth-placed Cottagers: "Hopefully 39 will be enough, but it is tough you can still go down.
"Hopefully we can go a bit higher, but first we will celebrate the three points."