The big man will not play when the No. 1 seed Orange meet Vermont in the first round on Friday evening, and coach Jim Boeheim labeled Onuaku "doubtful" should Syracuse advance to a second-round game on Sunday.
Onuaku, who injured his right leg during Syracuse's loss to Georgetown in the Big East tournament quarterfinal, said he feels better but has not practiced, run or ridden a stationary bike since the injury a week ago.
"It's getting better,'' he said. "The pain is down; the swelling is down. The strength is coming back.''
While his team, a top seed for the first time since 1980, prepared for Vermont, Onuaku spent his time with the team's athletic trainers, working on strength exercises and receiving varying types of treatment.
Relieved that the injury isn't as serious as he thought when he first fell to the floor -- it is a quad injury but not related to the quad tendon tear that required surgery in the offseason -- he admits to being understandably frustrated.
"It's hard for me, my senior year, the NCAA tournament, of course I want to be out there,'' he said. "But I don't have any control. I can only just take it one day at a time. The good thing is, it's getting better.''
Kris Joseph will start in Onuaku's place, not a drastic difference considering Joseph has been the first off the bench and has been a key contributor for Syracuse all season.
But Joseph gives up 2 inches and 55 pounds to Onuaku, changing the complexion of the Orange's very effective zone.
Equally dicey is what happens after Joseph.
The Orange have gone only seven deep all season but will have to call on freshman DaShonte Riley to fill the hole left by Onuaku.
Riley, who is 7-0, 233 pounds, has played 125 minutes this season.
"We've played that lineup with Kris 60 or 70 percent of the time, but without Arinze we don't have the depth or the size,'' Boeheim said. "It changes our rotation, how we can play and how we can attack the zone.''
Onuaku said he's spent the past week helping Riley as much as he can during practice and even more, trying to build up the freshman's confidence.
"They've talked to me about just getting back on defense, attacking the boards and just playing aggressive,'' Riley said. "I'll definitely be a little nervous but once I get up and down the court a little bit, I'll be fine.''
Before addressing Onuaku's injury, Boeheim made a point to clarify any misconception that he or anyone associated with his program had misled the selection committee with false information about the severity of Onuaku's injury.
After the bracket was revealed, committee chair Dan Guerrerro said that Onuaku's injury was not taken into account in regards to seeding because "the reports we received back from Syracuse were very positive in that regard,'' leading some to speculate that Syracuse massaged the news to preserve its No. 1 seeding.
"After he had the [MRI] on Friday, we thought there was a chance he would practice on Monday,'' Boeheim said. "When it got to be Sunday night, it was obvious to me that he wasn't going to be able to make practice. We never talked to the NCAA committee. I never did, our trainer, our doctor never did.''
Dana O'Neil covers college basketball for ESPN.com and can be reached at email@example.com.