Well then care to explain as to why this is, instead of just pointing it out.
most of the time players need first to play in challengers to improve their rankings enough to play on the main tour ... and quite often they havce success there.
As for "overrated" you know I've read MTF for 4 years now and I've read so many opinions of people supposedly well-informed (yes of course Filo V, but also Coocoocachoo now Martijn, or Nathaliia) who said that this or that guy was "only good for challengers" and not for main tour ... and that guy happened to surprise many people on the main Tour : Dodig, Rosol who both spent such a long time in early rounds of challengers you know (and Rosol was already the same kind of players according to many people I read), Golubev who was supposed according to Coocachoo only to be able to reach top-100 by luck or something like that and won Hamburg and Kuala Lumpur defeating very good guys, Bellucci in his time who had improved his ranking only through challengers then of couse was considered as a kind of "vulture" although the name didn't exist, Zeballos the same but still surprised everybody by reaching St Petersburg final and a few other good results on the main tour following his ones in challengers, Bogomolov, Janowicz was "Polish Querrey" for Nathaliia, Albert Ramos, Lukas Lacko
... so many guys you know I remember in my early years on MTF I trusted what these people said to predict a player's future then I realized that they were very often wrong (also in the other way actually predicting a great future to a player who never did it
a player "only good for challengers" I don't believe much in that now : I rather look at their results, if they manage to improve or not
Also tennis now is very physical and mental more than technical, and the differences in tennis levels are not as big as some people say, and when players get in a streak of confidence, they can usually follow it on the main tour.
As I said Lorenzi isn't just a challenger player, he's the only real vulture I know (with Sela) looking for every challenegr with a weak field to get a better ranking ... and still look at his results against supposedly "good players", he often makes very good results ! (of course the mention of his set won to Nadal on clay can be helpful for the evidence