Bielsa has won praise from across Europe for the way his Bilbao have performed this season.
Sa Pinto said: "Athletic are very strong, both home and away. The Spanish press talk of them being a second Barcelona. They play the ball out from the back, but when they don't have that option they also go long.
"They are a team with great mobility and creativity, who always try to play at a very high tempo. They are an aggressive, attacking side where up to six or seven players are ready to get on the end of a move. It seems like they are never tired, they give it everything."
The former Real Sociedad striker also hailed his counterpart Bielsa, saying: "Three of the best coaches in the world are in the Spanish league - Jose (Mourinho), Pep (Guardiola) and Bielsa.
"He has installed his own identity and a different type of play to which I faced from Athletic as a player."