It is normal to see another player of Juventus being positive.
Matuidi might not be infected by Rugani but he might be infected by other close people around him.
ALL players in ALL teams might be tested in a lot of short term periods in order to keep the pandemic trend in sport at it's lowest rates.
Valencia players are blaming Atalanta for the infection and I think they are right.Atalanta is a team of Bergamo which is one of the worst zones infected with the virus.Now 6 players of Valencia tested positive and they are right to be angry to Atalanta.Everything is locked down now in Italy and else where in Europe and so it should be.
In this case, actually we cannot blame it on anyone's side, of course Atalanta was also infected by someone else.
Compiled from theguardian.com that Matuidi is the second juventus player infected with this virus and I don't know whether dybala has been infected? because rugani and dybala are often together and surely there is direct contact between the two.