Linebacker Joe Staley was back in full force for Friday's final practice before hopping a charter flight to Dallas.
"It felt good to be back. The last few days were kind of crazy. I'm not used to not practicing so I felt good to be back with my teammates," said Willis.
The NFL's second-leading tackler sat out on Wednesday with a bit of a hamstring strain, and then ended up missing Thursday's practice when he fell ill.
"At this point, you aren't always going to be 100% physically but you've got to stay mentally sharp and get in your book," said Willis. "So, even when I was sick, I told coach that I wanted my playbook and the install so I could learn it."
The 49ers wanted their Pro Bowl backer to rest up and be in full force for Sunday, a game that will pit Willis against several players who he hung out with this past February in Hawaii.
"I had an opportunity to play with them and talk to them a lot at the Pro Bowl and they are a bunch of great guys," said Willis. "I look forward to playing them, and plus, the Cowboys were my favorite team growing up so I feel blessed to go get to play against them."
Willis is probable for Sunday's game, as are cornerback Tarell Brown, running back Michael Robinson, safety Mark Roman, tackle Barry Sims and tight end Delanie Walker.
Walker sat out last week's game with a shoulder injury, while Brown and Robinson suffered injuries in the Rams game. Roman, has been battling a groin injury, but started and played against St. Louis the entire game. Sims missed the last two games after injuring his ankle in the Seattle game.
Safety Dashon Goldson (knee) and wide receivers Arnaz Battle (foot) and Josh Morgan (groin) have been ruled out.
The Cowboys best cornerback is in question for Sunday's game as Pro Bowler Terence Newman was a late add to their injury report with a groin injury that kept him out of Friday's practice. Newman had prior surgery on his groin and missed six games before returning last week against the Redskins, when he promptly shutdown receiver Santana Moss.
It will be a game-time decision in terms of the starter at right guard this week. Tony Wragge has held down the position so far this season, but rookie Chilo Rachal has been rotating in for Wragge for a few series in the last two games. The 49ers coaching staff gave Rachal more reps at right guard this week and indicated that he could see his first start.