Hours after a Champions League loss away at Dinamo Zagreb, the German was relieved of his duties despite a busy summer of transfer activity at Stamford Bridge.
Graham Potter has since been appointed as Tuchel’s replacement, overseeing a 1-1 draw with RB Salzburg in his first game in charge.
Havertz was a key player under his compatriot, largely preferred to big-money signing Romelu Lukaku through the middle of the attack.
A season before the Belgian’s arrival, Havertz scored the winning goal in the 2021 Champions League final and later proved crucial in December’s Club World Cup victory.
While the 23-year-old has spoken of Potter in glowing terms, the forward admitted Tuchel’s exit came as a shock, echoing the thoughts of Antonio Rudiger.
Havertz told Kicker: “Me too [it surprised me]. Especially when you consider how we’ve played in the past year and a half and what we’ve won.
“With the current sixth place in the table, you can’t speak of a messed up start to the season, especially since we have many newcomers who first have to acclimatize. But football is very fast-moving, a lot can happen at any time.
“Our new coach has made a very good impression, we have a great squad. I think we are in for a good time.”