You talk as if the Big 10 and Nebraska have some high national respect level right now in basketball.

21 wins is not some magic number that gets us to the dance, especially with the remaining schedule. You are saying Nebraska goes 7-2. So who are the 2? Nebraska is in such a hole they pretty much have to win out, because they need the wins against the few decent teams they have, and absolutely can't afford to lose against the bad ones.
If Nebraska is # 5 in the conference, and ends up with 21 or more wins and has zero wins in quadrant 1, the committee members who don't care about the Big 10, representing the other conferences, are going to point that out, and will leave Nebraska out. They can not chose Nebraska if Nebraska has zero quadrant 1 wins over a team that has one or more, and has a higher RPI and SOS.
Below I listed conferences by RPI. I listed the number of teams in the top 30 in RPI currently in column 2. In the parenthesis for the first 7 conferences, I listed teams outside of the top 30 RPI, and listed their RPI/Strength of Schedule/Quadrant 1 wins best as I could figure (that number is an "at least #" for Q1 wins). The ones bolded have both an RPI and SOS better than Nebraska.
There are 36 at large bids. Lets assume there are no upsets, and that the automatic bid for the top 6 conferences goes to one of the teams in the top 30 RPI, that would leave, 23 teams in the top 30 RPI, all likely getting bids, leaving 13 at large bids. If you take the bolded teams that all have a higher RPI and SOS than Nebraska, just in the top 7 conferences, you get 15 teams.
Now look at the conferences below # 7 in RPI. Does the Mountain West get both Nevada and Boise in? What about if Bonnies get the A10 bid, does URI with an RPI of 9 at this point get left out? Does Buffalo get left out if they don't win their CCG?
Big 12 (#1) 5 teams (+
Texas 42/17/4, KSU 53/101/2)
ACC- (#2) 6 teams (+
FSU 41/62/2,
Syracuse 43/21/0, ND 62/52/2)
Big East-(#3) 6 teams (+
Providence 36/27/2,
Marquette 47/28/1)
SEC (#4) 7 teams (+
Missouri 38/22/3,
Georgia 51/60/3
Pac 12 (#5) 2 teams (+
USC 39/33/0,
UW 50/50/3)
Big 10 (#6) 3 teams (+
Michigan 37/65,
Maryland 52/52/1 Nebraska 66/80/0)
AAC- (#7) 2 teams (+
Temple 46/2/2, Houston 48/138,
SMU 54/61/2,
UCF 57/64/1)
____________________________________________________________
MV- (#8)- 0 teams (Probably 1 bid league)
MW- (#9) 2 teams
Nevada 13/51/1, Boise St. 34/87/0
A10- (#10) 1 team URI
9/25/1 (St. Bonn 49/73/2)
MAC- (#11) 1 Team
Buffalo 28/36/0
WCC- (#13) 0 teams (St. Marys 40/154/0, Gonzaga 56/160/
3)
Right now Nebraska is just in a bad spot, and Maryland isn't in much of a better one. Nebraska badly needs Michigan to move into the top 30 RPI before Selection Sunday.
Nebraska needs to beat Maryland, and have Maryland move into the top 30 by Selection Sunday. They have games at home vs Sparty, Michigan (oops we need Michigan to win), and a road game at Purdue. Not likely.
Nebraska needs to beat Minnesota to stay in the top 75 (they are currently 75th). They have games left including at Michigan (oops we need Michigan to keep winning), home to Sparty, at Purdue, and a bunch of games they can't lose, like 2 to Iowa and Indiana.
Now consider the four quadrants used by the committee. Nebraska's current record against each quadrant:
Q1: 0-5
Q2: 4-3
Q3: 2-0
Q4: 8-0
10 of 14 wins are from quads 3 and 4 currently

. Our remaining games:
Rutgers (twice) 179 (Q4/Q3)
Iowa 150 (Q3)
Wisconsin 133 (Q2)
Minnesota 75 (Q1)
Maryland 52 (Q2)
Illinois 172 (Q3)
Indiana 91 (Q3)
Penn State 135 (Q3)
That is NOT a tournament resume. Yes teams RPI numbers can change, but the conferences are pretty well set. Barring Michigan finishing in the top 30, and with some luck, a tourney win vs a top 30 Purdue or Michigan State (because again, we need Michigan to win the CC, if it ain't Nebraska), The odds are so stacked against Nebraska, because there are a hell of a lot more teams out there (from better conferences) with better arguments to get in, then there are spots available. Oh and 21 wins in the Big 10 this year, big freaking deal when over a third would be Q4 games.