The German striker only moved to the KC Stadium last summer, on a three-year deal for a fee of £2.6million from SC Paderborn, but has found game time and form hard to come by.
The 26-year-old made his first start of the season in Tuesday's Capital One Cup victory over Leyton Orient, but once again failed to impress alongside fellow frontman Matty Fryatt.
Bruce has now conceded that it may be in the best of interests of all concerned to look at putting another transfer in place before the current window closes.
He told the Hull Daily Mail: "The problem with Nick is his adaptation to the English game. He still hasn't quite grasped it.
"We thought he was maybe ready but unfortunately the physicality is something he finds difficult, especially playing in a cup tie. They're going to throw it into the box, scrap and fight, and that's exactly what they did. Unfortunately, he finds that a struggle.
"We'll see what the options are for him going forward but he's like anyone, he needs to play. He's not getting that here. There might be an opportunity (to move) but we'll see."