"This weekend is going to be absolutely critical for those guys at the top to get the job done before the enduros start," he said.
"The four at top will want to get as many points as they can before the three enduro races because anything can happen in those. I can't see any of them having any problems, but there are a lot of variables at play when you have co-drivers and much longer race distances.
"If you get knocked out of an enduro race it will severely hurt your championship chances, so getting as many points in the races before them is vital.
"If you have average runs it hurts, just look at where Shane is now in the championship compared to McLaughlin who has consistently been near the top.
"You want to go into the endures within striking distance of the leaders because there are a lot of points on offer over the next three races."
This season has seen two teams dominate and when four drivers with talent to burn are given the tools to showcase just how good they are, it was always going to be tight at the top of the leader board. DJR Team Penske had the pedigree to do well and with deep pockets were never in doubt of producing fast cars.
On the other hand, Triple Eight have dominated the championship over the past decade and there was no reason for them not to again.
"The seasons are all so different and hard to compare. At the beginning of the year I really thought Van Gisbergen's performance at round one was an indicator that he was just going to keep on dominating.
"Since then though his season has been tainted with a lot of ups and downs and hasn't had his own way. We've also seen the performance of Penske and they were always going to be a threat, it was just a matter of time.
"They've come on so strong so quickly that they've got a bit of a strangle hold on things at the moment especially with Scott [McLaughlin].
"Whincup is still at the top and fighting incredibly hard. The two teams [DJR Team Penske and Triple Eight] are now really strong and that's allowing us to see some great racing and great competition that I think will go down to the wire," said Murphy.
This weekend the four-time Bathurst winner reckons Chaz Mostert could be in with a chance to improve his title chances. The Rod Nash Racing pilot has had four pole positions and a couple of race wins at Sydney motorsport Park and has been very quick of late.
Penske will definitely be fast again this weekend and the circuit will suit McLaughlin and Coulthard and their cars as the track is long with a lot of corners. On current form you can't really go past McLaughlin as the man to come out on top at the end of the weekend.
