The young midfielder has spent just one season at the BayArena after moving from Bayern Munich last summer in search of first-team football.
As reported by Goal, his performances have caught the eye of the Premier League runners-up and Voller explained that there is a buyout clause in his contract.
|13/2||Liverpool are 13/2 with Bet365 to win the Premier League in 2014-15|
"Of course Emre has a clause in his contract now. We're still waiting for a decision. [A €12 million (£10m) return on a €5.5m (£4.5m)] investment would be lucrative business.
"But that is not the sticking point. We are of the opinion that Emre would do well with another year with us. Roger Schmidt has already spoken to him, he is really into the player.
"I am convinced that Can would be even better with Roger."
Bayern Munich have a buy-back clause with Emre and Voller says that the Bavarians want the player to spend another year in the Bundesliga before returning.
"Of course I spoke with Karl-Heinz Rummenigge on the subject," he continued. "Bayern think that another season at Leverkusen would be right for Emre."