De Miguel collided with Andorra goalkeeper Jesus Owono on Monday and was taken to intensive care. Spanish second-division club Tenerife confirmed his death on Tuesday morning.
A huge banner bearing his black-and-white photograph and the words "Forever Demi" - the nickname used by De Miguel's friends - hung behind a stage in the centre of the pitch at the Estadio Heliodoro Rodriguez Lopez.
After a video featuring footage of his Tenerife debut, supporters chanted: "De Miguel, we love you".
Players sat alongside representatives from every club in Spain's top two divisions, including Real Madrid director Emilio Butragueno, as tears flowed in the stands.
"To speak of you in the past tense is tremendously unfair," Gallego said, pausing repeatedly during his speech.
"It's still hard to believe that this has happened to us, Demi; you'll always be one of us."
"We're still struggling to come to terms with the fact that you won't be with us again," Gallego added.
Speeches by club directors were followed by a religious service during the 90-minute tribute in Santa Cruz de Tenerife.
Matches across Spain's divisions over the weekend observed a minute's silence in De Miguel's honour.