Given that these two are considered genuine contenders to lift this trophy next spring, there was no shortage of effort to gain early control of proceedings. Mainz began with slightly more purpose, as Nelson Weiper - the winning goalscorer against Zrinjski Mostar a fortnight ago - directed a promising close-range header straight at Tommaso Martinelli.
Fiorentina would soon silence the Mewa Arena, though, with La Viola’s first chance resulting in a vital goal, with Roberto Piccoli laying the ball off to Simon Sohm, who powered a first-time shot past Robin Zentner at his near post.
The Swiss international celebrated his first strike for Fiorentina with all due gusto, but he almost had the limelight snatched away by the provider, as Niccolo Fortini’s ball across goal nearly saw Piccoli slide in at the far post, only to be denied by Zentner’s legs.
An even better chance for a second Fiorentina goal presented itself on 38 minutes, when Dodo’s ball to Jacopo Fazzini saw the latter take a shot that was blocked at point-blank range by teenage defender Kacper Potulski.
The opening quarter-hour after the interval saw Fiorentina continue making the more promising moves down the right flank. Dodo charged down the right and played a ball back to Fazzini near the D, and his shot saw most of the away section rise in anticipation - but of all people, it was teammate Piccoli who blocked the effort.
Alongside Piccoli then firing wide under pressure from Zentner when put through on goal at an angle by Sohm, that may have been a factor in Fiorentina’s interim head coach, Daniele Galloppa, withdrawing him for Moise Kean just after the hour mark.
However, it was a switch from the other bench that would prove effective, as Paul Nebel made way for Benedict Hollerbach.
The summer arrival had barely been on the field two minutes before he sparked the move that led to an eye-catching equaliser, as Lee Jae-Sung was found in space and jinked into a more central position before finding Hollerbach with a clever pass into the box. Despite having Tommaso Martinelli bearing down on him, Hollerbach kept his nerve and found the net from six yards.
Unsurprisingly, given their superior freshness compared to most of the field, Hollerbach and Kean looked the liveliest of two evenly-matched teams.
Although the latter was flagged offside by the slimmest of margins when netting an apparent winner 10 minutes from time, it was Lee who landed the killer blow, heading in a cross from Kaishu Sano at the near post with almost the final kick of injury time, ensuring that they keep pace with Samsunspor and Celje at the summit of the league phase table.
Flashscore Man of the Match: Kacper Potulski (Mainz)