Pressure is mounting on Emery following last Saturday's 2-0 Premier League defeat away to high-flying Leicester City.
Arsenal are already eight points adrift of the top four after 12 matches and have won only once in their past seven games in all competitions.
While it is believed the club hierarchy remain behind Emery, who was appointed as Arsene Wenger's successor after the 2017-18 season, there is a growing discontent among Arsenal supporters who think a change is essential to save their season.
"It's true Arsenal are going through a tough spell," he told reporters on Monday. "But I haven't watched all their matches, so I can't talk about their game.
"They have a coach who is qualified who works well. When a club is having a difficult time, it's important to be united. I think he has enough experience to get them through this difficult spell.
"We have to get behind him and give him time to change things. I am not sure a change of manager will fix the problems."
Wenger, meanwhile, has lately been tipped to make a first return to management since leaving Emirates Stadium.
The 70-year-old told beIN SPORTS last week that he would be holding talks with Bayern Munich chairman Karl-Heinz Rummenigge over the prospect of succeeding Niko Kovac, but he then clarified on Monday that he was not in the running for the job.
Nice head coach Vieira still hopes to see his old manager make a return to the dugout, saying: "I would like to see him coaching again.
"Arsene has a big passion [for football]. I have never met another coach who spends more time watching football games, analysing their opponent's matches, talking about football.
"It's his passion, it's his life. So, I hope he can find another club to coach. It didn't work out with Bayern Munich; maybe it will work out with another team."