England right-back Trent Alexander-Arnold made his La Liga debut as Real Madrid earned a narrow win against Osasuna.

The summer signing from Liverpool had played five times for his new club at the Fifa Club World Cup, where they reached the semi-finals, under new boss Xabi Alonso.

But this was his Bernabeu bow, and he received a standing ovation when he was replaced by Dani Carvajal in the 68th minute.

Kylian Mbappe scored the only goal from the penalty spot as Real won their opening league game of the season in Alonso's first domestic match in charge.

The France international sent goalkeeper Sergio Herrera the wrong way after he had been fouled in the box.

Madrid, who finished second last season under Carlo Ancelotti, were dominant and could have scored more.

Defenders Dean Huijsen - also making his La Liga bow after a summer move from Bournemouth - and Eder Militao forced saves from Sergio Herrera from long range.

There were also debuts for £43m former Benfica left-back Alvaro Carreras and teenage midfielder Franco Mastantuono, a £38.5m recruit from River Plate.

Osasuna had Abel Bretones sent off in injury time for catching Goncalo Garcia.