The world's most expensive footballer arrived in Brazil on Thursday and will undergo surgery on a fractured metatarsal and a sprained ankle in Belo Horizonte on Saturday.
The doctor set to perform the operation said the typical recovery period is two and a half to three months, which would mean Neymar is back playing by mid-May at the earliest - just a month before Brazil kick off their World Cup campaign.
However, the trainer calmed nerves in his homeland by promising the 26-year would be ready for their opener against Switzerland on June 17.
"I am certain (he will be ready)," Fabio Mahseredjian told TV Globo. "I can affirm that there is sufficient time for him to be ready for the first match in the World Cup.
"Neymar will be there with very few games or training sessions under his belt, basically as if it is the start of the season.
"The surgery will mean he has a physical deconditioning, he will have lost some of the physiological effects that he gained during the season with PSG."
"I have no problem at all in saying that this could even be good for us because he won't have played a lot of games," Mahseredjian added. "Physiologically he will probably be in very good shape and we think psychologically as well."
The injury means the 26-year old will miss Brazil's friendlies later this month against World Cup hosts Russia and reigning champions Germany.
After their opening match against Switzerland, the five-times World Cup winners will then face Costa Rica and Serbia.
"Neymar is, of course, upset, sad, down," surgeon Rodrigo Lasmar said. "But he understands that there is no option now other than to recuperate and dedicate himself to recuperating so he can be good as soon as possible."
PSG confirmed the injury on Wednesday, ruling him out of the club's Champions League last-16, second leg, against Spanish holders Real Madrid.
The French side lost the first leg 3-1 in Madrid last month.
Neymar has scored 28 goals and provided 16 assists for the Ligue 1 leaders this season.
(Writing by Andrew Downie; Editing by Toby Davis/Nick Mulvenney)
