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Monday's match should have been easy for AC Milan, who were hoping to be Serie A leaders come Monday night after Inter Milan drew against Atalanta on Sunday. Instead, the unthinkable happened. Thiago Motta, a former Milan player and current Spezia coach, saw his team win in the last minute at San Siro as Spezia beat AC Milan, 2-1, on Monday.

The crazy match saw Milan take the lead in the first half with a goal from Rafael Leao, which came a few moments after Theo Hernandez's penalty kick mistake. The home team seemed to be in control of the match, only waiting to score the second goal. In the second half, however, the visiting team improved its attacking performance thanks to Kevin Agudelo's entry. 

Aguedelo completely changed the game for Spezia. On the other hand, AC Milan struggled with many absences. Key players such as Fikayo Tomori and Sandro Tonali were not included in the squad. Tomori got injured last week and will be out for the next month, missing crucial matches against Juventus this Sunday and the Milan derby in the first week of February. Tonali, the Italian midfielder, was suspended after the match against Venezia. 

AC Milan tried to change and win the game. Ante Rebic, Olivier Giroud and Junior Messias were subbed in later to play alongside Zlatan Ibrahimovic, who was already in the starting eleven. In the first minute of additional time, Rebic found space between the midfield and the defense and entered the edge of the penalty area.

The attacker was hit by the defender and the ball landd on the feet of Junior Messias, who scored what appeared to be the winning goal, but it was immediately disallowed by referee Marco Serra. Serra had whistled a foul on Rebic without giving the advantage, making an obvious mistake, and for this reason he apologized to the whole AC Milan team, realizing he made a crucial mistake. 

Things got worse for Milan. In the waning seconds, a Spezia counterattack found the home team unbalanced as they were desperately looking for the winning goal, and so Emmanuel Gyasi found himself alone in front of the goalkeeper and scored the late winner.

Here's a look:

After losing the match, AC Milan coach Stefano Pioli spoke to DAZN: "The referee made a mistake, he made a serious mistake, he also apologized but unfortunately it went like this. Everything went wrong tonight. But this has to give us a lot of energy to react immediately." 

AC Milan will travel to face Juventus in Turin on Sunday, a key game for the Scudetto and Champions League races.