The 49-year-old is refusing to get his hopes up over the prospect of bringing the former Villarreal striker back to Brazil
The 28-year-old, who has enjoyed two previous spells with the Brazilian giants, was rumoured to be interested in returning to the Porto Alegre-based club for a third spell, with club president Giovanni Luigi admitting his eagerness to make the move a reality.
However, while Dunga admits the striker - who now plays for Qatari outfit Al Rayyan - would be a welcome addition at any club, the former Brazil boss is worried that any bid for the former Villarreal forward could yet fall through.
"Any club would have Nilmar," he told reporters at a press conference. "But it would be very difficult if we dreamt of signing him, and he did not arrive. The trauma would be higher."
Meanwhile, president Luigi confirmed the striker was on their radar, but admitted it would be "very difficult" to make the dream a reality.
"We are always monitoring Nilmar," he added. "He has a great affection for the club, but it's very difficult to make it happen."