Holding a three-goal cushion from their first-leg away-day victory – Fiorentina’s joint-biggest continental win of the campaign – La Viola found themselves in a comfortable position at kick-off.
However, the two-time runners-up almost saw their advantage cut inside five minutes, as Afimico Pululu benefitted from a kind bouncing ball, only to tamely shoot straight at Luca Lezzerini.
Fiorentina responded well with a positive spell, but soon fell behind on the night in the 23rd minute, courtesy of Mazurek, who received the ball on the charge and guided home at the second attempt after Lezzerini had got an arm to the initial low strike.
The Polish side had never overturned a first-leg defeat in five previous attempts, but they cut the deficit to just one goal on the stroke of half time, thanks in large part to a significant deflection off Pietro Comuzzo that saw Mazurek’s drilled effort loop agonisingly over Lezzerini.
Introduced for the second half, it wasn’t long before David de Gea was picking the ball out of the net, as a deft Pululu lay-off allowed Mazurek to sweep home from close range, completing his hat-trick and levelling the tie just four minutes after the restart.
A pair of alterations from Paolo Vanoli saw an upturn in Fiorentina’s performance after the hour mark, yet clear-cut chances remained elusive for the hosts heading into the final minutes of the 90.
And with no further goals from the visitors in regulation time, the game headed to extra time, a scarcely believable prospect ahead of kick-off.
The contest was taking its toll as both sides were forced into bringing off injury-stricken substitutes, yet the tie remained on a knife-edge after a goalless first period of extra time.
With the prospect of penalties looming large, Fiorentina profited from a goalkeeping error as Sławomir Abramowicz came out to punch the ball, allowing Nicolò Fagioli to try his luck from the edge of the box, where he sent a half-volley beyond the shot-stopper’s reach.
Jaga needed a response, but they were dealt another blow when substitute Moise Kean turned home from a corner.
Remarkably, De Gea was deceived by a long-range strike from Jesús Imaz, sparking late hope in the 118th minute, yet it was not to be for the dogged Polish side, who ultimately fell short as Bernardo Vital received a second yellow for unsportsmanlike behaviour at the death.
Defeat ends a run of three consecutive competitive wins for La Viola, who did just about enough to see off Jaga, setting up a last-16 tie against one of the top two league phase sides in either Strasbourg or Raków Częstochowa.
Meanwhile, after progressing to the quarter-finals in last season’s Conference League, Jagiellonia can take plenty of positives from their efforts tonight, but they will ultimately not be repeating that feat this year.
Flashscore Man of the Match: Bartosz Mazurek (Jagiellonia Białystok)