Sarri has repeatedly questioned the mentality of his team, a tactic often employed by Mourinho during the season he was sacked at the club.
They are currently one point and two places off the top four.
"I understand that a manager has to stick with his views and opinions, even sometimes against his own players' thinking - because maybe he's right - but I'm sure that Sarri is very nervous," said Paddy Power ambassador Petit.
"His body language in a recent press conference showed this, as did what he did with Guardiola on Sunday.
"Things like this shouldn't happen, and when they do you show everyone - fans, journalists, players - that you're losing the plot. It reminds me a bit of the dark times under Jose Mourinho."