Voller 'can't imagine' Alonso leaving Leverkusen in the summer
Taking over with the club near the foot of the table last season, Alonso has supercharged Leverkusen, who are eight points clear atop the Bundesliga table and on track for a first-ever league title.
Alonso's Leverkusen are unbeaten in 32 games in all competitions this season, with only four draws.
When asked about the manager's future, Voller told Bild: "I can't imagine him going anywhere else in summer at the moment."
Voller played at Leverkusen before becoming coach and then sporting director, a role which he held for almost two decades until 2022, when he took on the same job in the German national team in 2022.
Along with being a board member and a club ambassador, Voller is a regular at Leverkusen games and is often seen sitting alongside the club CEO Fernando Carro.
"It could happen at some point that he goes to another club, but I can't imagine it this summer," he said.
Voller said even if Alonso delivered the title to Leverkusen, "it won't be over, it continues".
"I don't think there will be a big exodus. The majority will stay, you can always go one better next year," he said.
"But first we need to focus on closing out this season."
The 63-year-old named Liverpool, whose coach Jurgen Klopp will step down at season's end, alongside Bayern and Real Madrid as likely destinations.
Simon Rolfes, who replaced Voller as sporting director in 2022, said on Sunday he was "sure" Alonso would not leave in the summer.
"One thing is the contract, the other is how comfortable he feels," he said.
"He knows we will have a top team next year."
Alonso extended his deal at Leverkusen until 2026 before the start of the season.