The Oklahoma Sooners became the fifth different AP number-one team this season Monday afternoon, but by the end of the day they were the fifth different AP number-one team to suffer an upset.

Having moved up from second to first in the Associated Press Top 25 just hours earlier, Oklahoma went into the half down six points in Ames. The Sooners managed to turn up the offensive output in the second half, but could not slow the home team, and now the state of Iowa has seen three of its teams upset a different AP number-one team, The Associated Press noted.

 Oh, how the mighty have fallen! It has not been an easy year for No. 1 ranked teams this season.

A photo posted by SportsCenter (@sportscenter) on Jan 18, 2016 at 9:03pm PST

Iowa State could not bottle up Oklahoma's dynamic guard duo of Buddy Hield and Isaiah Cousins, as the two combined for 53 points. However, the Cyclones held the rest of the team to 24 points. Iowa State, on the other hand, had three players score at least 20 points and outrebounded Oklahoma 43-32.

"Basketball is alive and well here," Georges Niang said at a postgame press conference after leading Iowa State in scoring with 22 points. "Basketball is at an elite level in Iowa."

Like its in-state rival Iowa, Iowa State avenged an earlier loss. The Cyclones and Sooners opened their Big 12 schedule against one another, and it was the latter that won that meeting.

The win bring Iowa State two games off the Big 12 leaders with two games against Kansas, two against West Virginia, and one against Baylor left on their schedule. Oklahoma dropped to second place, but still figures to have an inside track for an NCAA Tournament one-seed at this point.

Hield added to his impressive season thus far, but the postseason has proven time and time again that teams who rely on one or two superstars often falter.

"We came ready to play," Hield said in his postgame comments. "But Iowa State had more fight than us."