Additionally, wide receiver Joe Adams (calf) and defensive tackle Frank Kearse (knee) were waived/injured.
Stewart is focused on a return to action for Week 7, the earliest he will be eligible to return from the PUP list.
"I can spend all my energy preparing myself for (Week 7). That's the timeframe that I have to be back," Stewart said. "I just have to heal up. I'm just taking it day by day like I've been – being there for my teammates. Just bringing as much positive energy as I can."
Head coach Ron Rivera added: "Right now, the best move is to put him on PUP. When he's ready, following the rules, we'll get him out here and ready to go. Until then, he'll continue to rehab. He's made some big strides, some real good things have happened; it's just not going to happen soon enough."
Rivera is hopeful fullback
"Mike Tolbert has made strides, and we most certainly aren't counting him out for Week 1," Rivera said. "We'll see how he progresses in the next couple days and then we'll start making plans as far as how we are going to game plan for Seattle.
Kugbila's rookie season is over before it ever really got started. The fourth-round draft choice was a spectator for the vast majority of training camp and preseason.
"We had to make a tough decision on Edmund. The young man has worked so hard," Rivera said. "You get excited about the young man, but this last little situation – the tweak with the knee and all that – in the long term, with our medical staff, they just really feel that this was the best thing for him.
"We're looking more toward the future with him."