Chelsea are closing in on the signing of Augsburg full-back Baba Rahman after having a £17.5million ($27million) bid accepted by the Bundesliga club.

The Blues have been in the market for a new full-back after the sale of Filipe Luis back to Atlético Madrid left them with just Cesar Azpilicueta at left-back.

Augsburg rejected an initial offer of around €20m ($22m) for the player they signed from Greuther Furth only last summer for £1million but reports in the German media say they have now agreed to a bid of 25million euros ($27m), which also contains significant bonuses.

"Both clubs are still working on fine-tuning but we hope the agreement will be finalised soon," Rahman's agent, Sascha Empacher, told the Guardian.

Chelsea boss Jose Mourinho, who is preparing his side for the Community Shield meeting with FA Cup winners Arsenal on Sunday, has confirmed that Chelsea are in the market for new additions to the squad.

"We are trying to sign a left-back," he said. "We have only one [César Azpilicueta]. We are trying."

Chelsea were first alerted to the Rahman's promise by their former manager, Avram Grant, who coaches Ghana. The 21-year-old was part of the squad who reached the final of the Africa Cup of Nations earlier this year, losing on penalties to Ivory Coast.

The Israeli retains close connections to the Stamford Bridge hierarchy and rates Rahman as one of his best players. Arsenal and Manchester City were among the other English clubs to have expressed an interest in signing him earlier this summer, while Atlético and Roma had also asked to be kept informed.

Having begun his career in Ghana at Accra-based Dreams FC, Rahman has enjoyed a meteoric rise and was nominated as the best left-back in his first season in the Bundesliga, losing out to Bayern Munich's Juan Bernat.