This is not true. When a reporter uses a source, it can be someone who has direct knowledge of what is going on but does not want his or her name revealed for some reason.
I do not generally allow unnamed sources to be used at my paper, but there are occasions when you have someone who you know to be reliable, you go with it if you can't get them or anyone else to go on record. We used to have a couple of sources who told us things but did not want their names revealed because of the position they held.
That doesn't mean that Pelissero's source is legitimate, but just because he's using one also doesn't mean the information is illegitimate. I do not know much about this sports reporter, so I can't say whether he just throws things at a wall and claims that he got it from a source.