Neil Magny failed a USADA drug test ahead of Saturday's co-main event at UFC Rochester, forcing the welterweight to withdraw from his fight against Vicente Luque.
Magny announced on Instagram Tuesday that he tested positive for a banned substance.
"On Saturday, May, 11, 2019, I received an email from USADA stating that I have failed an 'out of competition drug test' due to the banned substance Di-Hydroxy-LGB-4033," Magny posted.
The 31-year-old has been replaced by UFC newcomer Derrick Krantz for Saturday's co-main event.
Magny (21-7) previously fought in November, losing to Santiago Ponzinibbio. He owns a 14-6 record in the UFC and holds notable victories over Kelvin Gastelum and Johny Hendricks.