Bayer Leverkusen have signed Slovenia international Kevin Kampl from Borussia Dortmund on a five-year contract.
With South Korea international Son Heung-Min having moved from Leverkusen to Tottenham on Friday, the Bundesliga club have acted fast to bring in another midfielder.
Kampl, 24, arrives from Dortmund, whom he joined from FC Salzburg in January 2015.
It means he will spend a second spell at his hometown club and is also reunited with his former Salzburg coach Roger Schmidt, who tried to lure him to Leverkusen last winter.
"I am delighted to return to Leverkusen," Kampl told the club's official website. "To take to the field in the Bundesliga and Champions League is fantastic."
Schmidt said: "We would have loved to sign him last winter. It delights me even more that it worked out six months later."
Voller described Kampl as a versatile midfielder who would increase Leverkusen's options. He added: "We are very happy that Kevin has decided to join us. He is very versatile, quick and has the special quality of being able to get his teammates into good positions.''
Offiziell: Pierre-Emile Hojbjerg (20) wechselt zu Schalke 04! Leihgeschäft bis Ende dieser Saison, danach zurück zum FCB. ^M.Hörwick
- FC Bayern München (@FCBayern) August 28, 2015
But Leverkusen's hopes of bringing in midfielder Pierre-Emile Hojbjerg on loan from Bayern Munich were dashed after he opted to move to Schalke instead.
Leverkusen had been poised to reach an agreement to sign Denmark international Hojbjerg, 20, on a season-long deal, according to reports, before Schalke stepped in.