The 25-year-old Spaniard was just three days into his career as a professional rider, having joined the Caja Rural-Seguros RGA team, when he returned the positive sample for the anabolic steroid.
He was provisionally suspended by the UCI in January and Caja Rural swiftly rescinded his contract. This week he was added to the UCI's list of sanctions for anti-doping rule violations and his ban, effective from the date of the test, will run until the 25th October 2019, by which point he'll be nearly 28.
Gallego protested his innocence when news of the positive test emerged in January, claiming he was the victim of supplement contamination.
"At the news, my reaction could only have been what it was: incredulity," he wrote in an open letter on the Biciciclismo website. "I have never taken stanozolol. What's more, after asking doctors, given that I didn't even know what type of substance it is, I learned that it is a product much better suited for a body builder than a professional cyclist and, furthermore, it's a product that stays in the system for many weeks. In my case, it's illogical to think I could have used that product to improve my performances.
"I understand perfectly that there will be many who don’t want to believe in my innocence, but I'm in no doubt about it," he said. "After checking once more all the supplements I have used in recent years, I am more than certain that stanozolol doesn't appear on any of the labels. Therefore, the only option I have is to assume that I have been the victim of a laboratory contamination."
"For me, it's obvious that if I didn't take it knowingly, and if it's not on the labels, I am a victim. And I need everyone's support to prove it."
Gallego impressed on the Spanish amateur scene, where he was ranked number one before earning a deal with Radio Popular in 2014. He earned his contract with Caja Rural after catching the eye at last year's Route du Sud, where he finished seventh on the queen stage and went on to finish seventh overall behind the likes of Alberto Contador and Nairo Quintana.