On September 3, 2014, Fabbri signed a three-year, two way entry-level contract with the Blues but returned to the Storm for his final year of major junior hockey. He was invited to participate in the 2015 World Junior Ice Hockey Championships where he suffered an ankle injury during the quarter-finals against Denmark and was held to only 30 games for the OHL season. Fabbri returned to the lineup after missing two months in a 5–2 loss to the Sarnia Sting on March 9, 2015. He would bounce back a few games later with a five-point night against the Windsor Spitfires in a 9–3 win. The Storm qualified for the 2015 OHL playoffs where they were eventually eliminated in the Western Conference Semifinals by the Sault Ste. Marie Greyhounds. At the time, Fabbri was named the 10th best forward in Guelph Storm's history with 171 points in 147 regular season games.