"I thought our focus was a little off," UNM coach Steve Alford said.
In contrast, "passion" and "belief" carried Harvard, according to coach Tommy Amaker.
The Crimson (20-9) advance to meet No. 6 seed Arizona on Saturday, having produced the school's biggest basketball victory. Harvard is a capable team, as shown by a December win at California and a one-point loss at Saint Mary's.
But this obviously is a major blow to New Mexico. The Lobos emerged from a tough Mountain West with regular-season and tournament titles and believed this was the year they would break through in the NCAA Tournament.
Alford instead was outcoached by Amaker during a week when Alford received a new 10-year contract. Harvard clearly was the more poised team throughout the second half and particularly down the stretch.
No. 14 seeds now have a 17-98 record vs. No. 3 seeds since the tournament expanded to 64 teams in 1985. Weber State claims two of those victories, under coach Ron Abegglen in 1995 and 1999.
The Crimson shot 52.4 percent from the field and held Lobos guard Kendall Williams, the Mountain West player of the year, to eight points on 1-of-6 shooting.
"They made shots; they just did," Alford said. "I don't know how else to say it."
Because of their defense, the Lobos won nine games this season when they shot less than 40 percent. But they could not keep up with the Crimson.
With all five starters returning, New Mexico will be the favorite in an expanded MW that includes Utah State. But it will be a long offseason for the Lobos, dealing with the disappointment of underachieving in the NCAA Tournament.