The Blues sold Hazard, the brother of first-team star Eden Hazard, to Gladbach last year.
It was claimed they had an option to buy back the Belgian if he impressed in the Bundesliga.
Hazard, 23, has turned heads this season with his performances at the Borussia-Park, leading to speculation that he could return to west London in the future.
And while Eberl insists that there is no clause with Chelsea, he conceded the club would have to consider a big-money bid.
"There is no clause," he told German newspaper Express.
"(But) there is also no end of anything. I want to state that there is no contractual content.
"But we don't need to make a secret of it. If we get a top player from Chelsea, then Chelsea of course will think about this player again and again and the possibility (of signing him).
"But actually they're not active."
Hazard has scored four goals for Gladbach this season, which includes the opener in their narrow 2-1 defeat to Barcelona in the Champions League last month.
Gladbach are in Manchester City's Champions League group this season and host Pep Guardiola's side in November, having already lost 4-0 at the Etihad.