Mainz maintained its perfect UEFA Conference League record after substitute Lee Jae-Sung struck deep into stoppage time to complete a 2-1 comeback win over Fiorentina on Thursday.

The host, which had won both of its previous group matches, started with confidence but was caught out midway through the first half when Danny da Costa's misplaced pass gifted Fiorentina possession. Simon Sohm finished with a precise low strike to put the visitors ahead. Mainz goalkeeper Robin Zentner then produced a fine save to deny Roberto Piccoli and keep his team within reach before halftime.

After the interval, Mainz emerged with greater intent and quickly found its equalizer through substitute Benedikt Hollerbach, who started and finished a sharp attacking move just minutes after coming on. The goal reignited belief among the home fans, while Fiorentina, led by interim coach Daniele Galloppa, began to lose composure. The Italians still had a chance to retake the lead when Moise Kean headed over from close range midway through the half.

As the match entered its closing stages, Mainz pressed for a winner. Its persistence paid off in the fifth minute of added time, when another substitute combination broke the deadlock. Kaishu Sano's cross from the right found Lee, whose glancing header nestled into the far corner to seal the victory.

The result gives Mainz its third straight win in Europe and keeps it unbeaten after three games, placing it third in its group on goal difference behind the leading pair. Fiorentina remains under pressure to find consistency ahead of its next fixture against AEK Athens.

"It was one of those magical nights," said Mainz coach Bo Henriksen. "We're happy to celebrate a little with our fans. It was a strong opponent today, but we always believed in ourselves. For me, the most important thing was that we showed heart, and we did."