"They really wanted him to be there, but when it came down to it, he just isn't mentally or emotionally ready to appear on TV yet," a friend of Morgan's told the New York Post.
In Morgan's absence on the 40th anniversary special, his 30 Rock co-stars Tina Fey and Alec Baldwin paid tribute to him with a special "Tracy Morgan Moment." (Watch below.) Morgan was a series regular on Saturday Night Live from 1996 to 2003.
Morgan was critically injured when his limo collided with a Walmart tractor-trailer in New Jersey in June. Comedian James "Jimmy Mack" McNair was killed in the crash. In October, Morgan's lawyer said he may never again perform in public.
A federal judge denied an attempt by Kevin Roper, who was driving the tractor-trailer, to delay a civil lawsuit from Morgan against Walmart. Roper says he plans to appeal the ruling, because he believes the lawsuit will have a negative impact on his right to a fair trial in the criminal case against him, according to The Wrap.
Watch Fey and Baldwin's tribute to Morgan here: