Which violation would cause an athlete in Stage 2 to incur a financial penalty?

An athlete in Stage 2 would incur a financial penalty for a second positive test. In the context of substance abuse policies in the NFL, a second positive test indicates a more significant infringement of the league's rules, suggesting a pattern of behavior that needs to be addressed more seriously.

The first positive test is typically treated as a warning, focusing on education and opportunities for rehabilitation. However, when an athlete tests positive a second time, it signals ongoing issues and a disregard for the rules, leading to stricter consequences, including financial penalties. This approach aims to deter repeated violations and encourage compliance with the league's standards on substance use.

In contrast, the other options involve scenarios that do not automatically trigger financial penalties. A first positive test is more about intervention than punishment, a team trade request falls under contractual and team management matters that do not necessarily relate to substance abuse policy, and missing team practices could lead to disciplinary actions but does not specifically incur financial penalties without further context of league rules.