Lawrence Phillips -- Victim's Grandma Forgives NFL Star ... 'I'm Not Angry, I'm Sad'

The grandmother of the man allegedly killed by ex-NFL star Lawrence Phillips tells TMZ Sports ... she's not mad at him -- saying, "If [my grandson] was going to stay in jail for 80 years, maybe this was better."

As we previously reported, Phillips -- the #6 overall pick in the 1996 NFL Draft -- is the main suspect in the murder of his prison cellmate Damion Soward in Kern Valley State Prison in California.

We spoke with Damion's grandmother who told us several interesting things, including:

1) Damion's 1st cousin is former NFL wide receiver R. Jay Soward (a 1st round pick in 2000).
2) Damion told her he recently did 9 months in the hole at another prison after being caught with a weapon.

As far as how she feels about Phillips, she told us ... "I'm not angry. I'm sad for Damion. I love him and I'm sorry this happened to him."