Let's see Koevermans was able to crack the Dutch national team who have always had good strikers.
Sure while the Eredivisie as a whole isn't as strong as Serie A, playing with AZ and PSV, Koevermans played against some good CBs at Ajax, Twente, etc. plus let's not forget in European competition.
And while Nelson Rivas is a good player I'm sure, he only played 16 matches in 4 years with Inter. Didn't Stevanovic play at Inter too?
In the end, I'm sure Koevermans doesn't fear Nelson Rivas.