Karim Benzema, Sergio Ramos and Eden Hazard were all absent at the Santiago Bernabeu but Casemiro stepped up in their place.
His first double as a Real player proved the difference amid a three-goal flurry in the second half, during which Luuk de Jong had briefly pulled Sevilla level.
“Two goals for him is very unusual,” said Real Madrid coach Zinedine Zidane.
His team were largely underwhelming, at times reverting to the stodgy days of last season when they struggled for goals under Julen Lopetegui, who was this time in the dug-out of Sevilla.
Yet given those missing, the opposition and the performance, this might be the kind of victory that could prove crucial to Madrid winning the title in May.
“It makes the win even more important,” said Zidane. “It’s only three points but we needed them and we got them by suffering.”
Sevilla stay fourth, eight points off the top while Atletico Madrid in third are now the same margin behind after falling to a surprise 2-0 loss away at Eibar.
Barca can reclaim first place on Sunday by beating Granada at Camp Nou, where Quique Setien will be overseeing his debut game since being appointed coach early last week.
Setien has said he will not be satisfied if his team win while playing badly, but Zidane is likely to be less choosy.
His side are now 17 games unbeaten, a streak that included them winning the Spanish Super Cup in Saudi Arabia last weekend.
Ramos, who is still recovering from an ankle injury, paraded the club’s latest trophy on the pitch before kick-off.
Benzema came on in the second half after shaking off a dead leg but Ramos and Hazard need more time to recover.
Gareth Bale was not even in the squad, despite training on Friday. Bale missed the trip to Jeddah through illness.
“He picked up a knock the other day,” said Zidane. “Only because of that.”
– Sevilla struggle for goals –
Lopetegui was back at the Santiago Bernabeu for the first time since he was sacked by Real last season, 138 days after they appointed him.
“I haven’t even stopped to think about it,” Lopetegui said. “The only emotion I wanted to feel is to win here.”
His Sevilla side arguably deserved more too but converting impetus into goals has been their problem all season, and so it proved again.
De Jong thought he had scored when he was given a suspicious amount of space in the area to head in from a corner and VAR showed his marker Eder Militao had been blocked, albeit only by a small, but seemingly deliberate, step from Nemanja Gudelj.
Marcelo was lucky not to concede a penalty for a shirt-pull.
Sevilla were controlling the midfield and denying their opponents routes through to the front three. Yet 12 minutes into the second half, some creative brilliance saw the hosts take the lead.
Sergio Reguilon, bought by Sevilla from Real Madrid last year, scuffed his clearance and after Casemiro muscled through on the edge of the area, Luka Jovic found him again with a deft backheel. Casemiro chipped the ball in and pointed at Jovic in celebration.
Sevilla could have wilted but instead they equalised, only to concede again five minutes later.
First, Raphael Varane, Casemiro and Marcelo all missed tackles and after Munir El Haddadi stumbled, De Jong took over, banging the ball into the far corner.
Yet parity was short-lived as Casemiro nodded in Lucas Vazquez’s cross from a standing start after being given too much space by Jules Kounde.
Toni Kroos might have added a third for Madrid late on and Vazquez almost gifted Sevilla an equaliser after a dreadful backpass. Youssef En-Nesyri, signed from Leganes on Friday, flashed wide.
Atletico put in two of their best showings of the season at the Spanish Super Cup but any hopes of a boost were dashed at Ipurua, where Eibar secured a deserved win.
Esteban Burgos tapped in at the back post after 10 minutes before Edu Exposito’s drive in the 90th sealed it for Eibar and left Atletico even further adrift.
