Celtic assistant Johan Mjallby accepted that the attack by a fan on Neil Lennon at Tynecastle could give his manager doubts about his future.
The fan charged at Lennon after Celtic scored their second goal of a 3-0 victory over Hearts.
Asked if it could lead Lennon to quit, Mjallby said: "Of course nobody can blame him even if this didn't happen.
"He is shaken right now. But, for all our sakes, we are desperate for him to continue doing his work."
In January, a package addressed to Lennon containing bullets was intercepted at a sorting office in Country Antrim.
Then, in March, the club confirmed Lennon was under 24-hour security surveillance after a suspicious package was intercepted at a Royal Mail sorting office in Ayrshire and the following month it emerged that Royal Mail intercepted a total of two "viable" parcel bombs.
"We obviously have to see how he is going to react to this," Mjallby said of the incident at Tynecastle.
"You can never know what the guy is going to have in his hand, so it is shocking and you are obviously worried about Neil's safety.
"He is okay, but he's shaken and it's a proper disgrace. However, he is his own man and loves what he is doing.
"You have seen scenes on the telly all over the world, but I haven't myself been involved in anything like this.
"Surely we all have to look into this? If you work in management, you should be secure when you are on the football pitch."
Indeed, the SPL, Scottish Football Association and Hearts have all launched investigations.
The 3-0 win ensured that Celtic go into the final day of the Scottish Premier League season a point behind Rangers and with a chance of winning the title.
Celtic right-back Mark Wilson was thankful that the off-the-field incident did not divert the players from their goal.
"It was such a good performance and hard place to come, but I understand that that is going to be the main talking point," he said.
"The main thing is we're still there and can put a bit of pressure on Rangers.
"We will put pressure on Rangers on Sunday and hope that something happens."
However, Wilson backed Lennon to overcome the latest incident.
"He's had to deal with a lot this season. He must have some strength of character to deal with things like this," said the defender.
"I've just never seen it before in a game environment and it is very hard take I would imagine for him, but he is a strong character.
"The fans are pretty close to the dugout anyway, but it shouldn't happen that they can break through security and have a go at the coaching team."