Gregg survived the Munich Air Disaster in 1958 and won widespread praise for his bravery after staying with the burning plane to help passengers to safety.
Now 79, the former Northern Ireland international had a 10-year stint with the Red Devils, making 247 appearances.
A £23,000 arrival from Doncaster in 1957, his only honour was an FA Cup runners-up medal in the emotional defeat to Bolton in 1958, just after the tragedy. Gregg missed the win over Leicester five years later due to injury.
Although there has been no official announcement, it is anticipated Gregg's game will take place at Windsor Park on May 15.