Nketiah came off the bench to grab his fourth goal in six games, then won a decisive penalty kick for victory over Barnsley.
Bielsa said: “Nketiah is a striker who scores goals.
“Some players get involved a lot in finishing moves, more than creating them. He is a finisher.
“He has good characteristics to combine with his team mates, to play in this side and give more options. He is a complete player.”