Juventus' shares fell by nearly 22% on Wednesday after being knocked out of the Champions League by Ajax.
The shares recovered slightly on the Milan stock market but were still down by 17% during the early trading.
Matthijs de Ligt scored with just over 20 minutes to go as the Dutch side came from 1-0 behind to win 2-1 at the Allianz Stadium - which meant they won the quarter-final tie 3-2 on aggregate.
This will not be good news for the Agnelli family, who are the founders of motor company Fiat and have been running the Serie A side since 1923.
Ajax's shares were up by 7.58% after their victory and this has now valued the club at £272million.
Cristiano Ronaldo had given his side the lead in the 28th minute when he was unmarked from a corner.
Then five minutes later Erik ten Hag's side were level as Hakim Ziyech's shot deflected into the path of Donny van de Beek who put the ball home.
De Ligt then powered a header past Wojciech Szczesny to give Ajax a shock semi-final place.
The Dutch side will play the winner of Manchester City and Tottenham's quarter-final who play their second leg on Wednesday night.
Barcelona knocked out Manchester United on Tuesday to book their semi-final place and will play either Liverpool or Porto in the next round.