Schumacher and Colombian Montoya, who raced in Nascar after leaving F1 and is now returning to the Indycar series, were often fierce competitors.
"We spoke once in the six years that we raced against each other," Montoya, 38, is quoted by the German news agency DPA.
"He was a competitor, not a friend. Formula one is very closed -- as a McLaren driver I couldn't just go and sit in the Ferrari motor home."
However, he obviously rated the German very highly, claiming that "The only time Ferrari did well was when Michael was there".
Similarly, he said that if Schumacher's return to F1 with Mercedes was not successful, it was the fault of the Brackley based team.
"He didn't just forget how to drive. It's how it has always been in formula one," Montoya insisted.
Beyond that, he said it is difficult to comment on the current state of the sport, as "For seven years I have not watched formula one".
"Maybe one or two races a year."