Chelsea scout Piet de Visser admits they're delighted with the progress of Tomas Kalas and Gael Kakuta on-loan at Vitesse Arnhem.

Kakuta, particularly, has turned his career around in the Eredivisie this season.

"The Chelsea players are closely followed," said De Visser to Voetbal International. "What is striking is that these guys in this first half of the season are progressing in special situations.

"Kalas, who has spent his whole life playing centre-back, is a revelation at right-back.

"Kakuta was by wrong choices nearly lost, but is making a remarkable comeback."