put (one) at a disadvantage
To cause one to be in an unfavorable position compared to others. John knew about the deal for weeks, but I'm just getting all of this information now—he's putting me at a disadvantage here! She was put at an immediate disadvantage playing against the top seeded tennis player in the first round of the tournament.
put somebody/be at a disadˈvantage
make it/be difficult for somebody to succeed: My lack of experience put me at a disadvantage in comparison with the other candidates for the job.