Spain coach has 'blind confidence' in Barca teen Yamal
The 16-year-old would become Spain's youngest ever player if he features against either Georgia or Cyprus next Tuesday.
But De la Fuenta did not reveal whether the youngster would play as Spain bid to get their European qualifying campaign back on track.
"Lamine appeared very good to me watching him on television, but working with him you realise even more his potential. He seems even better," De la Fuente told a press conference on Thursday.
"Currently, he's a very important player for us, he's here on his own merit. I have total confidence in him. I think he's a great player."
Spain are aiming to correct a poor start to their qualifying campaign, but their preparations have been overshadowed by the controversy of suspended federation president Luis Rubiales' unsolicited kiss of women's team midfielder Jenni Hermoso.
"Since the beginning of the training camp, I have only been thinking about football and Georgia, because I believe that we have the possibility of putting qualification on the right track. We are focusing exclusively on the match tomorrow," said De la Fuente.
La Roja are fourth in the Group A, nine points behind leaders Scotland, who beat them in Glasgow, although De la Fuente's side have played two fewer matches.