Borussia Dortmund have begun their preparations for next season with the signing of Bayer Leverkusen midfielder Gonzalo Castro.

The 27-year-old has signed a four-year deal at Signal Iduna Park after opting to leave Leverkusen following 286 Bundesliga appearances, joining a Dortmund side set for a major rebuild after Jurgen Klopp's departure.

Castro helped Leverkusen secure a UEFA Champions League qualifying place on Saturday – the final day of the campaign – but has chosen to join Dortmund, who will be playing in the Europa League.

His arrival at Dortmund will provide cover in the midfield should Ilkay Gundogan depart as is expected during the close-season.

"We are delighted to have signed Gonzalo Castro," sporting director Michael Zorc told the club's official website.

"He is an experienced, technically skilled midfielder, who can be used in different positions."