There was a study about coach changes - there is often a short term increase in performance, but rarely a long term one. Combine that with opponents and a small sample size - doubt it was Petke holding RSL back necessarily. There was a similar bump when Petke took over IIRC (maybe not as big).RSL was at 1.43 pts/gm under Petke and they are undefeated with 2.5 pts/gm in four games under Juarez. I know some of it is probably who they played, but still...
And obviously 2.5/gm is never going to last for any significant period of time.