Gilberto says Arsene Wenger's angry reaction to losing at West Ham United left all of Arsenal's players feeling 'scared'.
The Brazil international gave an insight into what occurred in the Arsenal dressing room after The Gunners went down to a late 1-0 defeat at Upton Park last Sunday.
Wenger was upset with West Ham counterpart Alan Pardew for the manner of his celebrations to Marlon Harewood's winning strike for The Hammers.
The French tactician refused to shake Pardew's hand, with both managers having been charged with improper conduct by The Football Association as a result.
Gilberto was left surprised by Wenger's reaction to Sunday's defeat, revealing the tense mood there was in the dressing after the game.
"There were no problems between Mr Wenger and the players because the problem didn't involve the players," Gilberto told the Brazilian media. "But the situation left us scared.
"We know the manager and we know that he is very polite and calm. Something very bad had happened to make him react like he did.
"After the game, Mr Wenger didn't talk to anyone. As it wasn't a problem involving the players, he decided not to discuss it with us."
The former Atletico Mineiro man believes Pardew's actions are to blame for Wenger's fury with their London rivals.
"I have seen it on TV many times and when West Ham scored, Pardew came to our bench to celebrate, but in a offensive way," he added.
"That made Wenger react like he did, and that is why he had to talk to Pardew about that celebration.
"He was p****d off about the way Pardew celebrated and, as I said, that was the reason he reacted that way.
"As I saw it on TV, Pardew said some words that he, as a manager, should have thought about before saying.
"He should have showed a little more respect. Of course, he could celebrate the goal, but not in the offensive way he did.
"That is what made Wenger react."