Chelsea manager Frank Lampard says goalkeeper Kepa Arrizabalaga needs support after the Spaniard's costly error in Sunday's 2-0 defeat by Liverpool in the Premier League.

Arrizabalaga became the world's most expensive goalkeeper when he joined Chelsea from Athletic Bilbao for 80 million euros ($94.92 million) in 2018 but has struggled to justify his huge transfer fee.

He was at fault for Liverpool's second goal on Sunday, directing a clearance straight into the path of Sadio Mane, who tapped the ball into an empty net.

"With the Kepa situation it's a clear mistake," Lampard said. "A clear mistake that has cost us because at that point we go on to have a penalty which we maybe score.

"Those fine margins change games at this level. We have to keep working, Kepa has to keep working. He has to have support around him, that's very clear."

The 25-year-old keeper was also criticized for his role in Brighton and Hove Albion's goal on Monday when he failed to stop Leandro Trossard's shot from outside the area.

"Kepa has to keep working, nobody tries to make mistakes in football, it is the nature of the game. You have to be strong and keep going," added Lampard, who also confirmed Willy Caballero would start in goal against Barnsley in Wednesday's League Cup game.