Both are having season-ending surgeries Tuesday. Phillips with his back and Nelson with his pectoral muscle.
The attitude of the Sooners has been "next man up" the entire time when discussing the injury situation. So who are the players that will need to step up?
DT Jordan Wade
Let's start with the obvious one. It has to be defensive tackle Jordan Wade, who has started the last two games in place of Phillips.
Wade is slowly coming along, but he's going to have to pick up his game considerably or else every team is going to run the ball right down OU's throat from this point going forward.
"He's a big, strong, physical guy," defensive lineman Chuka Ndulue said. "He looks peaceful and quiet when he's walking. But when he put that helmet on, he's a different animal.
"Being out there with him, he's grown up. He's finally being a student of the game and getting his mentality up and just understanding."
Wade will share time with Torrea Peterson, but it looks like Wade will get the bulk of the snaps.
One of the things OU used to pitch to Dominique Alexander was the prospect of early playing time. It obviously wasn't supposed to be this early, but it has happened.
Alexander had 19 tackles against Texas in his first collegiate start. He was everywhere on the field, but that wasn't always a good thing. Sometimes he was out of position or pushed back so far that he made some of the tackles.
He said Nelson has been a huge influence on him and helped him get ready for the Red River Rivalry. Alexander is improving, but he still has some freshman moments that can only be alleviated with experience.
You can't expect Alexander to be the quarterback of the defense and make all the calls. That job now is going to have to be done by Frank Shannon.
Never the most vocal guy around, Shannon is going to have to change his mentality on and off the field because he is going to be running the show.
Shannon had 16 tackles against Texas, but he said he knows he has to play better going forward.
The elephant in the room right now is Russell. With so much hype coming into the season, the junior college signee has made minimal impact this season and hasn't been seen the last four games.
Unlike some of the younger players on the line, Russell doesn't have time to grow and mature. He needs to be at that point now. From listening to OU defensive coordinator Mike Stoops, Russell is not at that point yet.
Stoops said Russell needs to be more consistent with how he practices in order to see more time on Saturdays. If Russell isn't going to show a sense of urgency right now, there's a strong chance he'll never reach his potential.