The odds are against (someone/something)
This idiom is used for situations in which a person or people are unlikely to succeed.
Let’s say you have a friend who wants to be a professional basketball player. S/he is so passionate and eager. S/he always talks about pursuing his/her dreams. His/Her career plans are all about basketball. Although everything seems perfect, you realize that s/he misses an important point. S/he is 5.6 feet tall (1.70 meters). Therefore, you think that the odds are against her in this point. It is not likely for her/him to pursue a carreer in basketball even though it is enough for the school team.
P.S. Odds mean probability.