Siena scraped a 2-2 draw in Vicenza and Albinoleffe caused a huge upset away to Reggina in the Serie B rescheduled games.
These matches were called off in Week 14 and 17 due to adverse weather conditions.
Second-place Siena were on the verge of a shock defeat at the Stadio Menti this afternoon, trailing 2-1 before Marrone snatched a last-gasp equaliser.
It puts the Tuscans six points behind leaders Novara and sends Atalanta back down to third.
Reggina were on the end of a huge upset on home turf when Albinoleffe came away with a 2-1 victory at the Granillo, which was also decided at the 88th minute.
Leffe climb to 22 points, now just six behind Reggina.
Reggina 1-2 Albinoleffe
Scorers: Girasole 17 (A), Acerbi 72 (R), Previtali 88 (A)
Vicenza 2-2 Siena
Scorers: Schiavi 25 (V), Sestu 43 (S), Misuraca 71 (V), Marrone 89 (S)