Gros competed in junior races until 2010. From 2010 to 2013 he mainly took part in the Alpine Cup. He achieved two second places and one victory in the 2012/13 season and thus achieved ninth place in the overall standings. He made his first World Cup race in December 2010 in Düsseldorf , which he finished with 68th place in the sprint. He got his first World Cup points in December 2011 in Rogla with the 20th place in the sprint. At the French cross-country skiing championship in 2012 in Bessans , he won bronze in the sprint. In January 2014 he reached his first podium in a World Cup race with third place in the sprint in Szklarska Poręba . At the 2014 Winter Olympics in Sochi , he came in 40th place in the sprint. He finished the 2013/14 season in 32nd place in the sprint ranking. At the Nordic World Ski Championships in Falun in 2015 , he came in tenth place in the team sprint. In the Sprint World Cup he reached 15th place in the 2014/15 season. After finishing second at the start of the 2015/16 season at the Sprint World Cup in Davos , he won the sprint at the Alpencup in Planica in January 2016 . A week later he took second place in the World Cup in the sprint and together with Renaud Jay in the team sprint. At the Ski Tour Canada he came 47th. He won his first World Cup victory in the sprint in Québec and finished fourth in the Sprint World Cup at the end of the season. In the 2016/17 season he took second place in the sprint at the Alpine Cup in Planica and, together with Lucas Chanavat, second place in the team sprint at the World Cup in Pyeongchang . At the Nordic World Ski Championships 2017 in Lahti he finished 31st in the sprint. The following year he ran at the Winter Olympics in Pyeongchang to 12th place in the sprint.
In the 2018/19 season Gros achieved three top ten placements, including third place in the sprint in Davos and 49th place at the World Cup final in Québec, 41st place in the overall World Cup and 14th place in the Sprint World Cup. At the season highlight, the Nordic World Ski Championships 2019 in Seefeld in Tyrol , she finished 14th in the sprint.