The only goal arrived in the 13th minute, when 17-year-old forward Owen Mira Chukwuemeka rose above Ángel Ortiz to head home a cross from a wide free-kick, beating Real Betis goalkeeper Diego Conde at his near post. Mira, a product of the Granada academy, signed a contract extension with the club running to 2031 earlier this year after attracting interest from Real Madrid, and started the friendly alongside several other first-team debutants from the Granada youth ranks.
Betis had started brightly and almost broke the deadlock inside five minutes, when Ángel Ortiz's low cross picked out Gonzalo Petit, only for goalkeeper Raúl Lizoain to make a smart save. The visitors continued to create chances after falling behind, with Morante heading over from a corner and Diego Llorente forcing another save from Lizoain, but they could not find an equaliser before half-time.
Conde's afternoon ended in the first half after a heavy collision with team-mate Llorente as the goalkeeper rushed off his line, leaving Llorente dazed but able to continue; Conde needed treatment for an arm injury and was replaced by Álvaro Valles. Betis improved after the break, with Pablo García forcing a save from Granada's goalkeeper, but a lack of composure in the final third meant the Sevilla side never truly threatened an equaliser.
Tempers flared as the game wore on, with four yellow cards shown to Betis players, and defender Natan was sent off in stoppage time after reacting to a heavy challenge. It capped a frustrating pre-season workout for a Betis side that returns to the Champions League this season and still has ground to make up before the competitive campaign begins.
Saturday's defeat was Betis's third pre-season friendly of the summer and the first in which they failed to win, following victories in their opening two warm-up matches.
Pellegrini fielded a heavily rotated side, giving minutes to fringe players including Marc Bartra, Marc Roca and Bellerín from the bench as he continues assessing squad depth ahead of a season that will also include Champions League football.
Granada, who finished mid-table in Segunda División last season, will take particular confidence from a display built largely around academy graduates. Referee José Luis Guzmán Mansilla took charge of a match that produced further flashpoints beyond Natan's dismissal, as both sides grew increasingly frustrated in the closing stages.
Line-ups:
Granada: Lizoain; Casadesús, Flores, Manu Lama, Puma; Dylan, Gumbau, Alemañ; Owen Mira, José Arnaiz, Chinaza. Also played: Maza, Luca Zidane, Stoichkov, Bourama, Diego Hormigo, Ángelo, Pascual, Diallo, Rodelas, Naasei, Gambín.
Coach: Pacheta.
Real Betis: Diego Conde; Ángel Ortiz, Diego Llorente, Valentín Gómez, Fran García; Gnagnoro, Corralejo; Morante, Fornals, Riquelme; Gonzalo Petit. Also played: Álvaro Valles, Marc Bartra, Marc Roca, Iker Losada, Pablo García, Bellerín, Rica, Deossa, Junior Firpo, Borja Alonso, Natan.
Coach: Manuel Pellegrini.
Goals: 1-0 Owen Mira (13').
Yellow cards: Diego Llorente (45+1'), Junior Firpo (66'), Natan (85').
Red card: Natan (90+3').
Referee: José Luis Guzmán Mansilla.