Tregaro was a prospective high jumper, who placed 10th in the final of the high jump at the 1996 World Junior Championships. His coach was Viljo Nousiainen. Nousiainen died in 1999. This left Tregaro and the young triple jumper Christian Olsson without a coach. This led to Yannick's decision to begin coaching, his first athlete being the young Olsson. This would go on to become a highly successful partnership.