The Black Cats defender, joined in the South Americans' squad by Sunderland's new signing Cristian Riveros, was part of Gerardo Martino's line-up for the 2-2 draw against Ivory Coast on Sunday, when they battled back from two goals down.
But Da Silva knows his side need to make improvements at the back before embarking upon a Group F campaign against Italy, Slovakia and New Zealand.
He said: We must reduce the errors in defence that's the only way we will do well in the World Cup. It leaves us worried about the two goals we conceded against Ivory Coast.
Paraguay complete their preparations with a friendly against Greece in Switzerland tonight.
By the time Da Silva and Riveros arrive back on Wearside, Sunderland manager Steve Bruce should have secured the services of a new goalkeeper.
Bruce has been on the look out for back up to Scotland No 1 Craig Gordon after informing Marton Fulop that he can leave this summer.
Coventry's Kieran Westwood has been under consideration, but Bruce is close to agreeing a deal for Belgian Under-21 Simon Mignolet.
Mignolet was shown around the Academy of Light and the Stadium of Light over the weekend although his club, St Truidense, and Sunderland have yet to agree a fee.