I am not super confident or anything (I almost never am - Furman gave me the cold shakes, especially once their freshman started hot, like he wanted to take it out on us that we didn't recruit him). But Illinois was also 4-5 in their last nine games coming into the tournament, with one of their wins down to the wire against Maryland. They took care of business against Penn, but VCU's point guard got hurt in the first minute which took some of the upset potential in that one, and then they got a nine seed conference rival in the regional final.
However ... winning that game against Houston in Houston turned my head. They did it with defense - I didn't watch enough of the game, or watch it closely enough, to know if it was more that Houston crapped the bed or if Illinois just smothered them with their size. But they seemed like they just took Houston's will away in the second half.
They weren't peaking coming into the tourney, but that Houston win might have altered their trajectory and given them new life. By the time you reach this round, of course, you are probably going to face somebody who can give you some problems.