Hilliard, an undrafted free agent who spent most of last year on injured reserve, spent time this spring working with the first-team defense while starting middle linebacker Blake Martinez continues his rehab from a torn ACL. It boded well for the prospects of the second-year player from Ohio State under the Giants' new regime.
In a tweet on Friday, Hilliard said he takes "full responsibility" for having the banned substance in his body.
"I have been informed by the NFL that I tested positive for a banned diuretic - Spironolactone (Canrenone)," Hilliard wrote. "After investigation, it became clear that I mistakenly took my partner's prescription medication instead of my own anti-inflammatory prescription. I am well aware of the NFL's zero-tolerance policy, and I take full responsibility for having a banned substance in my body."
Hilliard can participate in training camp practices and games. He is eligible to return for the team's Week 3 game Monday night against the Dallas Cowboys.
Hilliard was claimed off waivers by the Giants before the start of last season. He was placed on injured reserve in mid-October with an ankle injury that he suffered during practice.