The Italy striker underperformed against Bayer Leverkusen on Saturday and the former Germany international is not sure if he is suited to his new side's style of playBorussia Dortmund summer signing Ciro Immobile will justify his €19 million (£15.1m) price tag.
The Italy international, who was the top scorer in Serie A last season with Torino, made his Bundesliga debut on Saturday but failed to impress in a shock 2-0 defeat for BVB at home to Bayer Leverkusen.
Hamann argues that, while Immobile is by no means a poor player, the 24-year-old striker is ill-suited to Jurgen Klopp's counterattacking tactics.
"I'm not sure if he has very much value for Borussia," the former Germany international told Sky.
"He's a box player and, given the way Dortmund play, I don't know if he helps them."
Immobile, who has been capped four times by his country, netted 22 times in 33 appearances in Serie A last season.