To lead a college basketball game by 20 points and lose by 17 was more than maddening to Kansas University senior Nick Collison.

“It’s embarrassing,” Collison said Saturday afternoon after the No. 6-ranked Jayhawks saw a 44-24 first-half lead erode into a 91-74 loss to No. 1-ranked Arizona at Allen Fieldhouse.

“This is the most disappointing game I’ve ever played in,” Collison added. “To play like that the first half and lose by 30 the second half at home is unbelievable.”

Believe it.

The Jayhawks, who hit 64.7 percent of their first-half shots and forced 12 turnovers, made just 29 percent of their second-half shots and were outscored by the Wildcats, 52-22.

What at one point looked like it would be a stirring KU victory wound up the second-worst home loss in coach Roy Williams’ 15 years in Lawrence — worst since a 25-pointer to Missouri on Feb. 1, 1989. It tied for the seventh-worst KU loss in fieldhouse history.

“The first half we looked as good as anybody in America. The second half we looked like a team that can’t win another game the rest of the season,” Williams said.

Williams watched his team lose the biggest halftime lead of his career, surpassing the 10-point deficit that Iowa State overcame against the Jayhawks on Feb. 28, 1999.

Few could never have envisioned a KU loss was coming late in the first half. Not after the 6-foot-9 Collison banked in a three-pointer and Keith Langford converted an alley-oop dunk, giving KU a 20-point advantage four minutes before halftime.

Between the three and dunk was a wild pass from Arizona’s Luke Walton five feet over the head over teammate Salim Stoudamire, a sequence that had Wildcat coach Lute Olson shaking his head in disbelief.

Yet Arizona outscored KU 15-8 the rest of the half. Jason Gardner sliced the deficit to 52-39 just before halftime with a pair of free throws after an ill-advised foul deep in the Wildcat backcourt by Jeff Hawkins.

Stoudamire, who erupted for 32 points — 20 the second half — scored four points in Arizona’s 10-0 run to open the second half.

The Jayhawks missed seven straight shots and committed six turnovers before Collison cashed KU’s first bucket six minutes into the second half. At that point, the Jayhawks led 55-54.

It was Kansas’ last lead of the day.

The ‘Cats, who hit 11 of their first 15 second-half shots to KU’s four of 14, outscored KU 13-4, and led, 67-59, at 11:21. The closest Kansas came after that was five, 76-71, at 4:01.

The rest of the way, Arizona outscored KU 15-3.

“A total breakdown,” KU coach Williams said of the second half. “I have no idea how somebody can change their performance like that, but it’s part of the game.”

KU’s Langford scored 22 points off 9-of-12 shooting the first half. Yet he scored just five points the second half off 2-of-7 shooting.

All of it came against the same Arizona zone.

“They sagged in the lane a lot more,” Langford explained. “The second half they took chances on us missing outside shots.”

Collison, who scored 11 points off 5-of-6 shooting the first half, scored four the second half off 2-of-6 shooting.

“Maybe it was a tougher zone, but we weren’t attacking,” Collison said. “I had three guys in my lap the whole second half.”

“They clogged it up a little more, played it a little more aggressive,” said power forward Jeff Graves, who scored eight points in the first 5 1/2 minutes, but finished with nine points and four fouls.

Senior guard Kirk Hinrich (15 points, 6-of-17 shooting) missed seven of eight threes the second half.

He wasn’t alone: The Jayhawks hit just nine of 31 tries for 29 percent the fatal half.

“I have no problem with what we ran or tried to run. We were running things we’ve run for 15 years,” Williams said. “We didn’t make shots. We go to the free-throw line and don’t make free throws (four of 12). On six or seven possessions the second half, we stopped their initial shot, and they’d get the rebound and score.

“To me it’s got to be psychological,” he added. “There’s no tactic for stopping a guy dribbling the ball out of bounds (like Langford did early in second half). There’s no tactic going 4-for-12 from the line. Somehow I’ve got to be able to get to them that they can make plays.

“Part of coaching is how the kids are mentally, and we’re not very good.”

It gets no easier. No. 4 Texas invades Allen Fieldhouse on Monday for an 8 p.m. tipoff.

“I’m concerned. Who wouldn’t be after you shoot 64 percent the first half and 29 percent the second half?” Williams said. “I think everybody would be concerned.”