The Brazilian is set to miss both legs of the last 16 fixture and his exclusion from the squad will be a major blow for manager Thomas Tuchel in PSG's pursuit for a first-ever Champions League trophy.
The 27-year-old sustained a metatarsal injury to his right foot during a Coupe de France match in late January, and the initial diagnosis revealed that he would miss up to around 10 weeks of action.
Neymar also suffered a similar injury to his foot last February that kept him out of the remainder of the 2017-18 season, including the second leg of the Champions League defeat to eventual winners Real Madrid.
Not only will the forward miss the first leg away at Old Trafford, but he is also expected to be absent for the return leg at the Parc
“We have our identity as a team and it’s not easy to change a team’s identity.
"We play attacking football, we’re PSG, that’s what we’re used to – to create opportunities, it’s in our DNA.
“To change that is really difficult but I’m sure there will be times where we will defend deeply.”
Neymar's absence isn't the only injury blow to PSG, as fellow strike partner Edinson Cavani is also expected to be a doubt for the first leg with a thigh injury.
It leaves Kylian Mbappe as the only member of the usual attacking trio to start against the Red Devils.
When asked if Neymar's absence from the side is comparable to the likes of Lionel Messi or Cristiano Ronaldo missing for Barcelona and Juventus respectively, Tuchel replied: “Let me put it in another way, would Manchester United miss [Paul] Pogba if he was not there tomorrow, or [Marcus] Rashford?
"Of course they will, you cannot replace quality players like this, Neymar is one of the key players in Europe and we miss him a lot and now we miss a second key player with Edinson.”
PSG will travel to Manchester United on February 12 to contest the first leg of the round of 16