Girona, second after their second 4-2 win over Barcelona this season, trail Real Madrid by 13 points.
Dani Carvajal was sent off at the death for Real Madrid after appearing to elbow Kike Perez.
Real Madrid's defence has been badly depleted by injuries this season but in attack the coach has a host of other options.
Joselu headed Real Madrid in front in the first half and finished lethally early in the second to put his team in command against their mid-table opposition
Record 14-time champions Real Madrid were already through but secured top spot with an entertaining win over the visiting Italian champions
Jude Bellingham, the division's top scorer with eight goals, was at his unstoppable best once more in the final third.
Real Madrid lead with 21 points from eight games, a point ahead of Barcelona, who are in turn a point ahead of Girona.
Real Madrid eased to a 2-0 win over Las Palmas on Wednesday to overtake Barcelona and move second, but Catalan minnows Girona are the surprise La Liga leaders after after a 2-1 win at Villarreal
Real Madrid came from behind to beat Real Sociedad 2-1 and climb back to the top of La Liga on Sunday, maintaining their perfect start to the season.
Jude Bellingham, who joined Madrid from Borussia Dortmund in a $114 million transfer in June, opened his account with an exquisite finish after just six minutes.