Remarkably, the Delfini upset Vincenzo Montella's side in the reverse fixture way back in January, but haven't won another game since that 2-0 victory.
The Rossoneri look to hold all the cards, but should they draw and Fiorentina win, then it will be the Viola who qualify by right of a better head-to-head record. Fiorentina won 3-1 at the San Siro in November, then came back from 2-0 down to salvage a 2-2 draw in Florence last month.
Whoever loses out and finishes fourth will take up one of two Europa League places on offer. Udinese are in pole position to take the final slot, as they currently sit two points ahead of Lazio. Both sides face away games on the final weekend. Udinese travel to injury-ravaged Inter Milan, while Cagliari host Lazio.
Should Lazio finish just behind Udinese - for a third consecutive season, the Eagles have a second chance of qualifying through the Coppa Italia.
The Biancocelesti face AS Roma in next weekend's Derby della Coppa final, with the winners gaining entry to the Europa League. If Lazio were to finish ahead of Udinese, then triumph over the Giallorossi, it will be Udinese who qualify by right of finishing sixth.
Roma are four points behind Udinese, so their only hope of playing European football next season is by winning the cup.