The Manchester City summer signing struck the first goal of the game after 26 minutes to make it 10 goals in 19 caps for Spain, but Del Bosque still feels that the striker is playing within himself for the national team.
"He [Negredo] is a striker who doesn't play as well as his ability permits. He still hasn't discovered his full potential,” explained the 62-year-old to reporters.
Del Bosque also reserved words of praise for Andres Iniesta who set up Negredo’s opener in his home town of Albacete, before sharing his thoughts on Spain’s qualification for the finals in Brazil.
“He [Iniesta] is a great role model and we took him off in the last few minutes because he deserved an ovation from his home crowd," he added.
“It's practically a routine for us because we keep on qualifying for tournaments but we have to remember that it's an important success, because Spain were qualifying for tournaments long before me and my team arrived.
“It hasn't been easy, we had problems against smaller teams and we competed with a very good France team for the top spot, but we've managed to do it. We have qualified with austerity."
The former Real Madrid boss was also cagey on talk of a new contract with the world and European champions, explaining that a new deal was up to the wishes of the Spanish Football Federation (REFF).
“There's not much more to say, we have a very good relationship, and it will happen if the Federation wants it to happen."